diff --git a/__tests__/validate-package-json.test.ts b/__tests__/validate-package-json.test.ts
index ef18176ecd92..b8dd9b78771e 100644
--- a/__tests__/validate-package-json.test.ts
+++ b/__tests__/validate-package-json.test.ts
@@ -70,17 +70,15 @@ describe('packages', () => {
         packageJsonFile.content.name?.startsWith('@'),
       )
       .forEach((packageJsonFile) => {
-        if (packageJsonFile) {
-          // Unfortunately jest custom message do not exist in loops,
-          // so using an exception instead to show failing package file
-          // (see https://github.com/facebook/jest/issues/3293)
-          // expect(packageJsonFile.content.publishConfig?.access)
-          //  .toEqual('public');
-          if (packageJsonFile.content.publishConfig?.access !== 'public') {
-            throw new Error(
-              `Package ${packageJsonFile.file} does not have publishConfig.access: 'public'`,
-            );
-          }
+        // Unfortunately jest custom message do not exist in loops,
+        // so using an exception instead to show failing package file
+        // (see https://github.com/facebook/jest/issues/3293)
+        // expect(packageJsonFile.content.publishConfig?.access)
+        //  .toEqual('public');
+        if (packageJsonFile.content.publishConfig?.access !== 'public') {
+          throw new Error(
+            `Package ${packageJsonFile.file} does not have publishConfig.access: 'public'`,
+          );
         }
       });
   });
diff --git a/admin/new.docusaurus.io/functions/codesandbox.ts b/admin/new.docusaurus.io/functions/codesandbox.ts
index 650c45727e6b..6f7b8327decf 100644
--- a/admin/new.docusaurus.io/functions/codesandbox.ts
+++ b/admin/new.docusaurus.io/functions/codesandbox.ts
@@ -8,6 +8,5 @@
 import {createPlaygroundResponse} from '../functionUtils/playgroundUtils';
 import type {Handler} from '@netlify/functions';
 
-export const handler: Handler = async function handler() {
-  return createPlaygroundResponse('codesandbox');
-};
+export const handler: Handler = () =>
+  Promise.resolve(createPlaygroundResponse('codesandbox'));
diff --git a/admin/new.docusaurus.io/functions/stackblitz.ts b/admin/new.docusaurus.io/functions/stackblitz.ts
index bc6a84d31f5a..6e69c2ade829 100644
--- a/admin/new.docusaurus.io/functions/stackblitz.ts
+++ b/admin/new.docusaurus.io/functions/stackblitz.ts
@@ -8,6 +8,5 @@
 import {createPlaygroundResponse} from '../functionUtils/playgroundUtils';
 import type {Handler} from '@netlify/functions';
 
-export const handler: Handler = async function handler() {
-  return createPlaygroundResponse('stackblitz');
-};
+export const handler: Handler = () =>
+  Promise.resolve(createPlaygroundResponse('stackblitz'));
diff --git a/packages/create-docusaurus/src/index.ts b/packages/create-docusaurus/src/index.ts
index c1f592cefcd1..6523b9291766 100755
--- a/packages/create-docusaurus/src/index.ts
+++ b/packages/create-docusaurus/src/index.ts
@@ -65,20 +65,22 @@ async function askForPackageManagerChoice(): Promise<PackageManager> {
     .map((p) => ({title: p, value: p}));
 
   return (
-    (await prompts(
-      {
-        type: 'select',
-        name: 'packageManager',
-        message: 'Select a package manager...',
-        choices,
-      },
-      {
-        onCancel() {
-          logger.info`Falling back to name=${defaultPackageManager}`;
+    (
+      (await prompts(
+        {
+          type: 'select',
+          name: 'packageManager',
+          message: 'Select a package manager...',
+          choices,
         },
-      },
-    )) as {packageManager: PackageManager}
-  ).packageManager;
+        {
+          onCancel() {
+            logger.info`Falling back to name=${defaultPackageManager}`;
+          },
+        },
+      )) as {packageManager: PackageManager}
+    ).packageManager ?? defaultPackageManager
+  );
 }
 
 async function getPackageManager(
@@ -101,8 +103,7 @@ async function getPackageManager(
     (await findPackageManagerFromLockFile('.')) ??
     findPackageManagerFromUserAgent() ??
     // This only happens if the user has a global installation in PATH
-    (skipInstall ? defaultPackageManager : askForPackageManagerChoice()) ??
-    defaultPackageManager
+    (skipInstall ? defaultPackageManager : askForPackageManagerChoice())
   );
 }
 
@@ -215,7 +216,7 @@ async function getGitCommand(gitStrategy: GitStrategy): Promise<string> {
             logger.info`Falling back to code=${'git clone'}`;
           },
         },
-      )) as {command: string};
+      )) as {command?: string};
       return command ?? 'git clone';
     }
     case 'deep':
@@ -362,7 +363,7 @@ async function getSource(
     )) as {gitRepoUrl: string};
     let strategy = cliOptions.gitStrategy;
     if (!strategy) {
-      ({strategy} = await prompts(
+      ({strategy} = (await prompts(
         {
           type: 'select',
           name: 'strategy',
@@ -385,7 +386,7 @@ async function getSource(
             logger.info`Falling back to name=${'deep'}`;
           },
         },
-      ));
+      )) as {strategy?: GitStrategy});
     }
     return {
       type: 'git',
@@ -426,13 +427,13 @@ async function getSource(
   }
   let useTS = cliOptions.typescript;
   if (!useTS && template.tsVariantPath) {
-    ({useTS} = await prompts({
+    ({useTS} = (await prompts({
       type: 'confirm',
       name: 'useTS',
       message:
         'This template is available in TypeScript. Do you want to use the TS variant?',
       initial: false,
-    }));
+    })) as {useTS?: boolean});
   }
   return {
     type: 'template',
diff --git a/packages/docusaurus-logger/src/index.ts b/packages/docusaurus-logger/src/index.ts
index 6db95cdd1531..768cb8f9a0c2 100644
--- a/packages/docusaurus-logger/src/index.ts
+++ b/packages/docusaurus-logger/src/index.ts
@@ -9,10 +9,10 @@ import chalk from 'chalk';
 
 type InterpolatableValue = string | number | (string | number)[];
 
-const path = (msg: unknown): string => chalk.cyan.underline(`"${msg}"`);
+const path = (msg: unknown): string => chalk.cyan.underline(`"${String(msg)}"`);
 const url = (msg: unknown): string => chalk.cyan.underline(msg);
 const name = (msg: unknown): string => chalk.blue.bold(msg);
-const code = (msg: unknown): string => chalk.cyan(`\`${msg}\``);
+const code = (msg: unknown): string => chalk.cyan(`\`${String(msg)}\``);
 const subdue = (msg: unknown): string => chalk.gray(msg);
 const num = (msg: unknown): string => chalk.yellow(msg);
 
diff --git a/packages/docusaurus-mdx-loader/src/index.ts b/packages/docusaurus-mdx-loader/src/index.ts
index ad7887dcc77c..1b7f2be72344 100644
--- a/packages/docusaurus-mdx-loader/src/index.ts
+++ b/packages/docusaurus-mdx-loader/src/index.ts
@@ -21,7 +21,7 @@ export type LoadedMDXContent<FrontMatter, Metadata, Assets = undefined> = {
   /** As provided by the content plugin. */
   readonly metadata: Metadata;
   /** A list of TOC items (headings). */
-  readonly toc: readonly TOCItem[];
+  readonly toc?: readonly TOCItem[];
   /** First h1 title before any content. */
   readonly contentTitle: string | undefined;
   /**
diff --git a/packages/docusaurus-mdx-loader/src/loader.ts b/packages/docusaurus-mdx-loader/src/loader.ts
index 88fa1ecd5bdc..638a62566724 100644
--- a/packages/docusaurus-mdx-loader/src/loader.ts
+++ b/packages/docusaurus-mdx-loader/src/loader.ts
@@ -55,7 +55,7 @@ export type MDXOptions = {
   beforeDefaultRehypePlugins: MDXPlugin[];
 };
 
-export type Options = MDXOptions & {
+export type Options = Partial<MDXOptions> & {
   staticDirs: string[];
   siteDir: string;
   isMDXPartial?: (filePath: string) => boolean;
@@ -138,7 +138,7 @@ export async function mdxLoader(
 ): Promise<void> {
   const callback = this.async();
   const filePath = this.resourcePath;
-  const reqOptions = this.getOptions() ?? {};
+  const reqOptions = this.getOptions();
 
   const {frontMatter, content: contentWithTitle} = parseFrontMatter(fileString);
 
diff --git a/packages/docusaurus-mdx-loader/src/remark/headings/index.ts b/packages/docusaurus-mdx-loader/src/remark/headings/index.ts
index 51b0cb6c7bbd..98aaa37f7552 100644
--- a/packages/docusaurus-mdx-loader/src/remark/headings/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/headings/index.ts
@@ -17,7 +17,7 @@ export default function plugin(): Transformer {
   return (root) => {
     const slugs = createSlugger();
     visit(root, 'heading', (headingNode: Heading) => {
-      const data = headingNode.data || (headingNode.data = {});
+      const data = headingNode.data ?? (headingNode.data = {});
       const properties = (data.hProperties || (data.hProperties = {})) as {
         id: string;
       };
@@ -36,7 +36,7 @@ export default function plugin(): Transformer {
         // Support explicit heading IDs
         const parsedHeading = parseMarkdownHeadingId(heading);
 
-        id = parsedHeading.id || slugs.slug(heading);
+        id = parsedHeading.id ?? slugs.slug(heading);
 
         if (parsedHeading.id) {
           // When there's an id, it is always in the last child node
diff --git a/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts b/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
index 9c9f2004ba7d..59e1b4117bf5 100644
--- a/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
@@ -110,8 +110,9 @@ async function processLinkNode(node: Link, context: Context) {
   if (!node.url) {
     // Try to improve error feedback
     // see https://github.com/facebook/docusaurus/issues/3309#issuecomment-690371675
-    const title = node.title || (node.children[0] as Literal)?.value || '?';
-    const line = node?.position?.start?.line || '?';
+    const title =
+      node.title ?? (node.children[0] as Literal | undefined)?.value ?? '?';
+    const line = node.position?.start.line ?? '?';
     throw new Error(
       `Markdown link URL is mandatory in "${toMessageRelativeFilePath(
         context.filePath,
diff --git a/packages/docusaurus-mdx-loader/src/remark/utils/index.ts b/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
index b0314d7a2349..3bf275085bf5 100644
--- a/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
@@ -15,7 +15,7 @@ export function stringifyContent(node: Parent): string {
 }
 
 export function toValue(node: PhrasingContent | Heading): string {
-  switch (node?.type) {
+  switch (node.type) {
     case 'text':
       return escapeHtml(node.value);
     case 'heading':
diff --git a/packages/docusaurus-migrate/src/__tests__/index.test.ts b/packages/docusaurus-migrate/src/__tests__/index.test.ts
index 8eea0cd15849..306f7e394a12 100644
--- a/packages/docusaurus-migrate/src/__tests__/index.test.ts
+++ b/packages/docusaurus-migrate/src/__tests__/index.test.ts
@@ -19,22 +19,22 @@ async function testMigration(siteDir: string, newDir: string) {
   await migrateDocusaurusProject(siteDir, newDir, true, true);
   expect(
     writeMock.mock.calls.sort((a, b) =>
-      posixPath(a[0] as string).localeCompare(posixPath(b[0] as string)),
+      posixPath(a[0]).localeCompare(posixPath(b[0])),
     ),
   ).toMatchSnapshot('write');
   expect(
     mkdirpMock.mock.calls.sort((a, b) =>
-      posixPath(a[0] as string).localeCompare(posixPath(b[0] as string)),
+      posixPath(a[0]).localeCompare(posixPath(b[0])),
     ),
   ).toMatchSnapshot('mkdirp');
   expect(
     mkdirsMock.mock.calls.sort((a, b) =>
-      posixPath(a[0] as string).localeCompare(posixPath(b[0] as string)),
+      posixPath(a[0]).localeCompare(posixPath(b[0])),
     ),
   ).toMatchSnapshot('mkdirs');
   expect(
     copyMock.mock.calls.sort((a, b) =>
-      posixPath(a[0] as string).localeCompare(posixPath(b[0] as string)),
+      posixPath(a[0]).localeCompare(posixPath(b[0])),
     ),
   ).toMatchSnapshot('copy');
   writeMock.mockRestore();
diff --git a/packages/docusaurus-migrate/src/frontMatter.ts b/packages/docusaurus-migrate/src/frontMatter.ts
index 2d03fb0e40e5..6ec040296d74 100644
--- a/packages/docusaurus-migrate/src/frontMatter.ts
+++ b/packages/docusaurus-migrate/src/frontMatter.ts
@@ -40,12 +40,7 @@ export default function extractMetadata(content: string): Data {
   lines.slice(0, -1).forEach((line) => {
     const keyValue = line.split(':') as [string, ...string[]];
     const key = keyValue[0].trim();
-    let value = keyValue.slice(1).join(':').trim();
-    try {
-      value = JSON.parse(value);
-    } catch (err) {
-      // Ignore the error as it means it's not a JSON value.
-    }
+    const value = keyValue.slice(1).join(':').trim();
     metadata[key] = value;
   });
   return {metadata, rawContent: both.content};
diff --git a/packages/docusaurus-migrate/src/index.ts b/packages/docusaurus-migrate/src/index.ts
index 81f31e6b874c..165c7c2fd32f 100644
--- a/packages/docusaurus-migrate/src/index.ts
+++ b/packages/docusaurus-migrate/src/index.ts
@@ -474,7 +474,7 @@ async function migrateVersionedDocs(
     versions.reverse().map(async (version, index) => {
       if (index === 0) {
         await fs.copy(
-          path.join(siteDir, '..', context.v1Config.customDocsPath || 'docs'),
+          path.join(siteDir, '..', context.v1Config.customDocsPath ?? 'docs'),
           path.join(newDir, 'versioned_docs', `version-${version}`),
         );
         await fs.copy(
@@ -551,7 +551,9 @@ async function migrateVersionedSidebar(
       const newSidebar = Object.entries(sidebarEntries).reduce(
         (topLevel: SidebarEntries, value) => {
           const key = value[0].replace(versionRegex, '');
-          topLevel[key] = Object.entries(value[1]).reduce((acc, val) => {
+          topLevel[key] = Object.entries(value[1]).reduce<{
+            [key: string]: Array<string | {[key: string]: unknown}>;
+          }>((acc, val) => {
             acc[val[0].replace(versionRegex, '')] = (
               val[1] as SidebarEntry[]
             ).map((item) => {
@@ -565,7 +567,7 @@ async function migrateVersionedSidebar(
               };
             });
             return acc;
-          }, {} as {[key: string]: Array<string | {[key: string]: unknown}>});
+          }, {});
           return topLevel;
         },
         {},
@@ -574,33 +576,32 @@ async function migrateVersionedSidebar(
     }
     await Promise.all(
       sidebars.map(async (sidebar) => {
-        const newSidebar = Object.entries(sidebar.entries).reduce(
-          (acc, val) => {
-            const key = `version-${sidebar.version}/${val[0]}`;
-            acc[key] = Object.entries(val[1]).map((value) => ({
-              type: 'category',
-              label: value[0],
-              items: (value[1] as SidebarEntry[]).map((sidebarItem) => {
-                if (typeof sidebarItem === 'string') {
-                  return {
-                    type: 'doc',
-                    id: `version-${sidebar.version}/${sidebarItem}`,
-                  };
-                }
+        const newSidebar = Object.entries(
+          sidebar.entries,
+        ).reduce<SidebarEntries>((acc, val) => {
+          const key = `version-${sidebar.version}/${val[0]}`;
+          acc[key] = Object.entries(val[1]).map((value) => ({
+            type: 'category',
+            label: value[0],
+            items: (value[1] as SidebarEntry[]).map((sidebarItem) => {
+              if (typeof sidebarItem === 'string') {
                 return {
-                  type: 'category',
-                  label: sidebarItem.label,
-                  items: sidebarItem.ids.map((id) => ({
-                    type: 'doc',
-                    id: `version-${sidebar.version}/${id}`,
-                  })),
+                  type: 'doc',
+                  id: `version-${sidebar.version}/${sidebarItem}`,
                 };
-              }),
-            }));
-            return acc;
-          },
-          {} as SidebarEntries,
-        );
+              }
+              return {
+                type: 'category',
+                label: sidebarItem.label,
+                items: sidebarItem.ids.map((id) => ({
+                  type: 'doc',
+                  id: `version-${sidebar.version}/${id}`,
+                })),
+              };
+            }),
+          }));
+          return acc;
+        }, {});
         await fs.outputFile(
           path.join(
             newDir,
@@ -702,12 +703,12 @@ async function migrateLatestDocs(context: MigrationContext) {
 
 async function migratePackageFile(context: MigrationContext): Promise<void> {
   const {deps, siteDir, newDir} = context;
-  const packageFile = importFresh(`${siteDir}/package.json`) as {
+  const packageFile = importFresh<{
     scripts?: {[key: string]: string};
     dependencies?: {[key: string]: string};
     devDependencies?: {[key: string]: string};
     [otherKey: string]: unknown;
-  };
+  }>(`${siteDir}/package.json`);
   packageFile.scripts = {
     ...packageFile.scripts,
     start: 'docusaurus start',
diff --git a/packages/docusaurus-migrate/src/sanitizeMD.ts b/packages/docusaurus-migrate/src/sanitizeMD.ts
index 55bd803aea51..61e3904cb0aa 100644
--- a/packages/docusaurus-migrate/src/sanitizeMD.ts
+++ b/packages/docusaurus-migrate/src/sanitizeMD.ts
@@ -37,7 +37,7 @@ export default function sanitizeMD(code: string): string {
   const htmlTree = unified().use(parse).parse(markdownString);
 
   visit(htmlTree, 'element', (node: Element) => {
-    if (!tags[node.tagName as string]) {
+    if (!tags[node.tagName]) {
       (node as Element | Text).type = 'text';
       (node as Element & Partial<Omit<Text, 'type'>>).value =
         node.tagName + toText(node);
diff --git a/packages/docusaurus-module-type-aliases/src/index.d.ts b/packages/docusaurus-module-type-aliases/src/index.d.ts
index ccb4bf5706fc..cd6bf0d1c910 100644
--- a/packages/docusaurus-module-type-aliases/src/index.d.ts
+++ b/packages/docusaurus-module-type-aliases/src/index.d.ts
@@ -8,7 +8,7 @@
 declare module '@generated/client-modules' {
   import type {ClientModule} from '@docusaurus/types';
 
-  const clientModules: readonly (ClientModule & {default: ClientModule})[];
+  const clientModules: readonly (ClientModule & {default?: ClientModule})[];
   export default clientModules;
 }
 
diff --git a/packages/docusaurus-plugin-client-redirects/src/__tests__/writeRedirectFiles.test.ts b/packages/docusaurus-plugin-client-redirects/src/__tests__/writeRedirectFiles.test.ts
index 739c2f6a99b5..2ed5d2f1a1b1 100644
--- a/packages/docusaurus-plugin-client-redirects/src/__tests__/writeRedirectFiles.test.ts
+++ b/packages/docusaurus-plugin-client-redirects/src/__tests__/writeRedirectFiles.test.ts
@@ -17,7 +17,7 @@ import writeRedirectFiles, {
 // - https://github.com/facebook/docusaurus/issues/3886
 // - https://github.com/facebook/docusaurus/issues/3925
 describe('createToUrl', () => {
-  it('creates appropriate redirect urls', async () => {
+  it('creates appropriate redirect urls', () => {
     expect(createToUrl('/', '/docs/something/else')).toBe(
       '/docs/something/else',
     );
@@ -29,7 +29,7 @@ describe('createToUrl', () => {
     );
   });
 
-  it('creates appropriate redirect urls with baseUrl', async () => {
+  it('creates appropriate redirect urls with baseUrl', () => {
     expect(createToUrl('/baseUrl/', '/docs/something/else')).toBe(
       '/baseUrl/docs/something/else',
     );
@@ -43,7 +43,7 @@ describe('createToUrl', () => {
 });
 
 describe('toRedirectFilesMetadata', () => {
-  it('creates appropriate metadata trailingSlash=undefined', async () => {
+  it('creates appropriate metadata trailingSlash=undefined', () => {
     const pluginContext = {
       outDir: '/tmp/someFixedOutDir',
       baseUrl: 'https://docusaurus.io',
@@ -70,7 +70,7 @@ describe('toRedirectFilesMetadata', () => {
     );
   });
 
-  it('creates appropriate metadata trailingSlash=true', async () => {
+  it('creates appropriate metadata trailingSlash=true', () => {
     const pluginContext = {
       outDir: '/tmp/someFixedOutDir',
       baseUrl: 'https://docusaurus.io',
@@ -97,7 +97,7 @@ describe('toRedirectFilesMetadata', () => {
     );
   });
 
-  it('creates appropriate metadata trailingSlash=false', async () => {
+  it('creates appropriate metadata trailingSlash=false', () => {
     const pluginContext = {
       outDir: '/tmp/someFixedOutDir',
       baseUrl: 'https://docusaurus.io',
@@ -127,7 +127,7 @@ describe('toRedirectFilesMetadata', () => {
     );
   });
 
-  it('creates appropriate metadata for root baseUrl', async () => {
+  it('creates appropriate metadata for root baseUrl', () => {
     const pluginContext = {
       outDir: '/tmp/someFixedOutDir',
       baseUrl: '/',
@@ -142,7 +142,7 @@ describe('toRedirectFilesMetadata', () => {
     );
   });
 
-  it('creates appropriate metadata for empty baseUrl', async () => {
+  it('creates appropriate metadata for empty baseUrl', () => {
     const pluginContext = {
       outDir: '/tmp/someFixedOutDir',
       baseUrl: '',
diff --git a/packages/docusaurus-plugin-client-redirects/src/index.ts b/packages/docusaurus-plugin-client-redirects/src/index.ts
index 78d117c7ca28..237f3f099e9e 100644
--- a/packages/docusaurus-plugin-client-redirects/src/index.ts
+++ b/packages/docusaurus-plugin-client-redirects/src/index.ts
@@ -18,7 +18,7 @@ import type {PluginOptions, Options} from './options';
 export default function pluginClientRedirectsPages(
   context: LoadContext,
   options: PluginOptions,
-): Plugin<unknown> {
+): Plugin<void> {
   const {trailingSlash} = context.siteConfig;
 
   return {
diff --git a/packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts b/packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts
index 48c3395f728b..7b7981985443 100644
--- a/packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts
+++ b/packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts
@@ -89,6 +89,7 @@ describe.each(['atom', 'rss', 'json'])('%s', (feedType) => {
         },
         readingTime: ({content, defaultReadingTime}) =>
           defaultReadingTime({content}),
+        truncateMarker: /<!--\s*truncate\s*-->/,
       } as PluginOptions,
     );
 
@@ -128,6 +129,7 @@ describe.each(['atom', 'rss', 'json'])('%s', (feedType) => {
         },
         readingTime: ({content, defaultReadingTime}) =>
           defaultReadingTime({content}),
+        truncateMarker: /<!--\s*truncate\s*-->/,
       } as PluginOptions,
     );
 
diff --git a/packages/docusaurus-plugin-content-blog/src/__tests__/index.test.ts b/packages/docusaurus-plugin-content-blog/src/__tests__/index.test.ts
index 11b33cd2a183..384b7014c7ea 100644
--- a/packages/docusaurus-plugin-content-blog/src/__tests__/index.test.ts
+++ b/packages/docusaurus-plugin-content-blog/src/__tests__/index.test.ts
@@ -76,7 +76,7 @@ const getPlugin = async (
         editUrl: BaseEditUrl,
         ...pluginOptions,
       },
-    }) as PluginOptions,
+    }),
   );
 };
 
diff --git a/packages/docusaurus-plugin-content-blog/src/__tests__/translations.test.ts b/packages/docusaurus-plugin-content-blog/src/__tests__/translations.test.ts
index 62442bbf8151..a29ae6e3acb7 100644
--- a/packages/docusaurus-plugin-content-blog/src/__tests__/translations.test.ts
+++ b/packages/docusaurus-plugin-content-blog/src/__tests__/translations.test.ts
@@ -74,7 +74,7 @@ function getSampleTranslationFilesTranslated() {
 }
 
 describe('getContentTranslationFiles', () => {
-  it('returns translation files matching snapshot', async () => {
+  it('returns translation files matching snapshot', () => {
     expect(getSampleTranslationFiles()).toMatchSnapshot();
   });
 });
diff --git a/packages/docusaurus-plugin-content-blog/src/authors.ts b/packages/docusaurus-plugin-content-blog/src/authors.ts
index cf3bbe5c8522..4d8f7b90b3fb 100644
--- a/packages/docusaurus-plugin-content-blog/src/authors.ts
+++ b/packages/docusaurus-plugin-content-blog/src/authors.ts
@@ -44,7 +44,11 @@ const AuthorsMapSchema = Joi.object<AuthorsMap>()
   });
 
 export function validateAuthorsMap(content: unknown): AuthorsMap {
-  return Joi.attempt(content, AuthorsMapSchema);
+  const {error, value} = AuthorsMapSchema.validate(content);
+  if (error) {
+    throw error;
+  }
+  return value;
 }
 
 export async function getAuthorsMap(params: {
diff --git a/packages/docusaurus-plugin-content-blog/src/blogUtils.ts b/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
index 370ddeb50aa3..ee6742c7bff5 100644
--- a/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
+++ b/packages/docusaurus-plugin-content-blog/src/blogUtils.ts
@@ -264,7 +264,7 @@ async function processBlogSourceFile(
   const title = frontMatter.title ?? contentTitle ?? parsedBlogFileName.text;
   const description = frontMatter.description ?? excerpt ?? '';
 
-  const slug = frontMatter.slug || parsedBlogFileName.slug;
+  const slug = frontMatter.slug ?? parsedBlogFileName.slug;
 
   const permalink = normalizeUrl([baseUrl, routeBasePath, slug]);
 
@@ -323,7 +323,7 @@ async function processBlogSourceFile(
             defaultReadingTime,
           })
         : undefined,
-      truncated: truncateMarker?.test(content) || false,
+      truncated: truncateMarker.test(content),
       authors,
       frontMatter,
     },
diff --git a/packages/docusaurus-plugin-content-blog/src/index.ts b/packages/docusaurus-plugin-content-blog/src/index.ts
index a3dddc2404f5..2b0355a0f3f1 100644
--- a/packages/docusaurus-plugin-content-blog/src/index.ts
+++ b/packages/docusaurus-plugin-content-blog/src/index.ts
@@ -176,10 +176,6 @@ export default async function pluginContentBlog(
     },
 
     async contentLoaded({content: blogContents, actions}) {
-      if (!blogContents) {
-        return;
-      }
-
       const {
         blogListComponent,
         blogPostComponent,
@@ -500,11 +496,7 @@ export default async function pluginContentBlog(
     },
 
     injectHtmlTags({content}) {
-      if (!content.blogPosts.length) {
-        return {};
-      }
-
-      if (!options.feedOptions?.type) {
+      if (!content.blogPosts.length || !options.feedOptions.type) {
         return {};
       }
 
diff --git a/packages/docusaurus-plugin-content-blog/src/markdownLoader.ts b/packages/docusaurus-plugin-content-blog/src/markdownLoader.ts
index a5f3d4929889..add3e16682c2 100644
--- a/packages/docusaurus-plugin-content-blog/src/markdownLoader.ts
+++ b/packages/docusaurus-plugin-content-blog/src/markdownLoader.ts
@@ -34,5 +34,5 @@ export default function markdownLoader(
     finalContent = truncate(finalContent, markdownLoaderOptions.truncateMarker);
   }
 
-  return callback?.(null, finalContent);
+  return callback(null, finalContent);
 }
diff --git a/packages/docusaurus-plugin-content-blog/src/options.ts b/packages/docusaurus-plugin-content-blog/src/options.ts
index f6fa74e726bc..ff06c867dc9d 100644
--- a/packages/docusaurus-plugin-content-blog/src/options.ts
+++ b/packages/docusaurus-plugin-content-blog/src/options.ts
@@ -136,9 +136,6 @@ export function validateOptions({
   validate,
   options,
 }: OptionValidationContext<Options, PluginOptions>): PluginOptions {
-  const validatedOptions = validate(
-    PluginOptionSchema,
-    options,
-  ) as PluginOptions;
+  const validatedOptions = validate(PluginOptionSchema, options);
   return validatedOptions;
 }
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/translations.test.ts.snap b/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/translations.test.ts.snap
index a67e0081748c..b952835b06d0 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/translations.test.ts.snap
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/translations.test.ts.snap
@@ -90,13 +90,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc1 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc1 title",
+          },
           "id": "doc1",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc1 title",
           "slug": "any",
           "source": "any",
           "title": "doc1 title",
@@ -106,13 +108,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc2 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc2 title",
+          },
           "id": "doc2",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc2 title",
           "slug": "any",
           "source": "any",
           "title": "doc2 title",
@@ -122,13 +126,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc3 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc3 title",
+          },
           "id": "doc3",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc3 title",
           "slug": "any",
           "source": "any",
           "title": "doc3 title",
@@ -138,13 +144,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc4 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc4 title",
+          },
           "id": "doc4",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc4 title",
           "slug": "any",
           "source": "any",
           "title": "doc4 title",
@@ -154,13 +162,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc5 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc5 title",
+          },
           "id": "doc5",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc5 title",
           "slug": "any",
           "source": "any",
           "title": "doc5 title",
@@ -232,13 +242,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc1 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc1 title",
+          },
           "id": "doc1",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc1 title",
           "slug": "any",
           "source": "any",
           "title": "doc1 title",
@@ -248,13 +260,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc2 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc2 title",
+          },
           "id": "doc2",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc2 title",
           "slug": "any",
           "source": "any",
           "title": "doc2 title",
@@ -264,13 +278,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc3 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc3 title",
+          },
           "id": "doc3",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc3 title",
           "slug": "any",
           "source": "any",
           "title": "doc3 title",
@@ -280,13 +296,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc4 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc4 title",
+          },
           "id": "doc4",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc4 title",
           "slug": "any",
           "source": "any",
           "title": "doc4 title",
@@ -296,13 +314,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc5 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc5 title",
+          },
           "id": "doc5",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc5 title",
           "slug": "any",
           "source": "any",
           "title": "doc5 title",
@@ -374,13 +394,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc1 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc1 title",
+          },
           "id": "doc1",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc1 title",
           "slug": "any",
           "source": "any",
           "title": "doc1 title",
@@ -390,13 +412,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc2 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc2 title",
+          },
           "id": "doc2",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc2 title",
           "slug": "any",
           "source": "any",
           "title": "doc2 title",
@@ -406,13 +430,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc3 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc3 title",
+          },
           "id": "doc3",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc3 title",
           "slug": "any",
           "source": "any",
           "title": "doc3 title",
@@ -422,13 +448,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc4 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc4 title",
+          },
           "id": "doc4",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc4 title",
           "slug": "any",
           "source": "any",
           "title": "doc4 title",
@@ -438,13 +466,15 @@ exports[`translateLoadedContent returns translated loaded content 1`] = `
         {
           "description": "doc5 description",
           "editUrl": "any",
+          "frontMatter": {
+            "sidebar_label": "doc5 title",
+          },
           "id": "doc5",
           "lastUpdatedAt": 0,
           "lastUpdatedBy": "any",
           "next": undefined,
           "permalink": "any",
           "previous": undefined,
-          "sidebar_label": "doc5 title",
           "slug": "any",
           "source": "any",
           "title": "doc5 title",
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/cli.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/cli.test.ts
index bb1f1c70a071..55c50ab0cddf 100644
Binary files a/packages/docusaurus-plugin-content-docs/src/__tests__/cli.test.ts and b/packages/docusaurus-plugin-content-docs/src/__tests__/cli.test.ts differ
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
index 3e0f09010925..9a338c5bf9d2 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
@@ -119,7 +119,7 @@ function createTestUtils({
 
   async function testSlug(docFileSource: string, expectedPermalink: string) {
     const docFile = await readDoc(docFileSource);
-    const metadata = await processDocMetadata({
+    const metadata = processDocMetadata({
       docFile,
       versionMetadata,
       context,
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/index.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/index.test.ts
index 0d54d4bc1308..fd25cc85eef9 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/index.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/index.test.ts
@@ -54,9 +54,9 @@ const createFakeActions = (contentDir: string) => {
     addRoute: (config: RouteConfig) => {
       routeConfigs.push(config);
     },
-    createData: async (name: string, content: unknown) => {
+    createData: (name: string, content: unknown) => {
       dataContainer[name] = content;
-      return path.join(contentDir, name);
+      return Promise.resolve(path.join(contentDir, name));
     },
     setGlobalData: (data: unknown) => {
       globalDataContainer.pluginName = {pluginId: data};
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
index bcbaccfe1144..a3ddd11f843d 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
@@ -31,11 +31,11 @@ const defaultOptions = {
 };
 
 describe('normalizeDocsPluginOptions', () => {
-  it('returns default options for undefined user options', async () => {
+  it('returns default options for undefined user options', () => {
     expect(testValidate({})).toEqual(defaultOptions);
   });
 
-  it('accepts correctly defined user options', async () => {
+  it('accepts correctly defined user options', () => {
     const userOptions = {
       path: 'my-docs', // Path to data on filesystem, relative to site dir.
       routeBasePath: 'my-docs', // URL Route.
@@ -83,7 +83,7 @@ describe('normalizeDocsPluginOptions', () => {
     });
   });
 
-  it('accepts correctly defined remark and rehype plugin options', async () => {
+  it('accepts correctly defined remark and rehype plugin options', () => {
     const userOptions = {
       beforeDefaultRemarkPlugins: [],
       beforeDefaultRehypePlugins: [markdownPluginsFunctionStub],
@@ -100,7 +100,7 @@ describe('normalizeDocsPluginOptions', () => {
     });
   });
 
-  it('accepts admonitions false', async () => {
+  it('accepts admonitions false', () => {
     const admonitionsFalse = {
       admonitions: false,
     };
@@ -110,7 +110,7 @@ describe('normalizeDocsPluginOptions', () => {
     });
   });
 
-  it('rejects admonitions true', async () => {
+  it('rejects admonitions true', () => {
     const admonitionsTrue = {
       admonitions: true,
     };
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/translations.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/translations.test.ts
index 5d098e355fb7..a79409ba8d84 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/translations.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/translations.test.ts
@@ -30,7 +30,9 @@ function createSampleDoc(doc: Pick<DocMetadata, 'id'>): DocMetadata {
     unversionedId: 'any',
     version: 'any',
     title: `${doc.id} title`,
-    sidebar_label: `${doc.id} title`,
+    frontMatter: {
+      sidebar_label: `${doc.id} title`,
+    },
     description: `${doc.id} description`,
     ...doc,
   };
@@ -136,7 +138,7 @@ function getSampleTranslationFilesTranslated() {
 }
 
 describe('getLoadedContentTranslationFiles', () => {
-  it('returns translation files', async () => {
+  it('returns translation files', () => {
     expect(getSampleTranslationFiles()).toMatchSnapshot();
   });
 });
diff --git a/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts b/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
index 752a53d91edc..f3229ac46522 100644
--- a/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
+++ b/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
@@ -126,6 +126,6 @@ export function getDocVersionSuggestions(
   const latestVersion = getLatestVersion(data);
   const activeDocContext = getActiveDocContext(data, pathname);
   const latestDocSuggestion: GlobalDoc | undefined =
-    activeDocContext?.alternateDocVersions[latestVersion.name];
+    activeDocContext.alternateDocVersions[latestVersion.name];
   return {latestDocSuggestion, latestVersionSuggestion: latestVersion};
 }
diff --git a/packages/docusaurus-plugin-content-docs/src/client/index.ts b/packages/docusaurus-plugin-content-docs/src/client/index.ts
index 298ed4dcd9c9..bfc2bfd78cb0 100644
--- a/packages/docusaurus-plugin-content-docs/src/client/index.ts
+++ b/packages/docusaurus-plugin-content-docs/src/client/index.ts
@@ -34,9 +34,11 @@ const StableEmptyObject = {};
 // In blog-only mode, docs hooks are still used by the theme. We need a fail-
 // safe fallback when the docs plugin is not in use
 export const useAllDocsData = (): {[pluginId: string]: GlobalPluginData} =>
-  (useAllPluginInstancesData('docusaurus-plugin-content-docs') as {
-    [pluginId: string]: GlobalPluginData;
-  }) ?? StableEmptyObject;
+  (useAllPluginInstancesData('docusaurus-plugin-content-docs') as
+    | {
+        [pluginId: string]: GlobalPluginData;
+      }
+    | undefined) ?? StableEmptyObject;
 
 export const useDocsData = (pluginId: string | undefined): GlobalPluginData =>
   usePluginData('docusaurus-plugin-content-docs', pluginId, {
diff --git a/packages/docusaurus-plugin-content-docs/src/index.ts b/packages/docusaurus-plugin-content-docs/src/index.ts
index 982895957382..afbb809fb718 100644
--- a/packages/docusaurus-plugin-content-docs/src/index.ts
+++ b/packages/docusaurus-plugin-content-docs/src/index.ts
@@ -143,7 +143,7 @@ export default async function pluginContentDocs(
             )}".`,
           );
         }
-        async function processVersionDoc(docFile: DocFile) {
+        function processVersionDoc(docFile: DocFile) {
           return processDocMetadata({
             docFile,
             versionMetadata,
diff --git a/packages/docusaurus-plugin-content-docs/src/markdown/index.ts b/packages/docusaurus-plugin-content-docs/src/markdown/index.ts
index 5de4aae87f4d..9d846ef8d5c5 100644
--- a/packages/docusaurus-plugin-content-docs/src/markdown/index.ts
+++ b/packages/docusaurus-plugin-content-docs/src/markdown/index.ts
@@ -16,5 +16,5 @@ export default function markdownLoader(
   const fileString = source;
   const callback = this.async();
   const options = this.getOptions();
-  return callback?.(null, linkify(fileString, this.resourcePath, options));
+  return callback(null, linkify(fileString, this.resourcePath, options));
 }
diff --git a/packages/docusaurus-plugin-content-docs/src/options.ts b/packages/docusaurus-plugin-content-docs/src/options.ts
index 27b9118a718f..bd1cd5d70732 100644
--- a/packages/docusaurus-plugin-content-docs/src/options.ts
+++ b/packages/docusaurus-plugin-content-docs/src/options.ts
@@ -165,7 +165,7 @@ export function validateOptions({
     }
   }
 
-  const normalizedOptions = validate(OptionsSchema, options) as PluginOptions;
+  const normalizedOptions = validate(OptionsSchema, options);
 
   if (normalizedOptions.admonitions) {
     normalizedOptions.remarkPlugins = normalizedOptions.remarkPlugins.concat([
diff --git a/packages/docusaurus-plugin-content-docs/src/props.ts b/packages/docusaurus-plugin-content-docs/src/props.ts
index 8505d5de2cd2..7d27cebaa9b4 100644
--- a/packages/docusaurus-plugin-content-docs/src/props.ts
+++ b/packages/docusaurus-plugin-content-docs/src/props.ts
@@ -51,7 +51,7 @@ Available document ids are:
     } = docMetadata;
     return {
       type: 'link',
-      label: sidebarLabel || item.label || title,
+      label: sidebarLabel ?? item.label ?? title,
       href: permalink,
       className: item.className,
       customProps:
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
index 671c12cfe256..9f01f06347b7 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
@@ -463,7 +463,7 @@ describe('DefaultSidebarItemsGenerator', () => {
     expect(sidebarSlice).toMatchSnapshot();
   });
 
-  it('throws for unknown index link', async () => {
+  it('throws for unknown index link', () => {
     const generateSidebar = () =>
       DefaultSidebarItemsGenerator({
         numberPrefixParser: DefaultNumberPrefixParser,
@@ -499,7 +499,7 @@ describe('DefaultSidebarItemsGenerator', () => {
         },
       });
 
-    await expect(generateSidebar).rejects.toThrowErrorMatchingInlineSnapshot(`
+    expect(() => generateSidebar()).toThrowErrorMatchingInlineSnapshot(`
             "Can't find any doc with ID foo.
             Available doc IDs:
             - intro"
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
index d0a530bbd7f2..7dc7111dbe0a 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
@@ -26,7 +26,7 @@ describe('processSidebars', () => {
   function createStaticSidebarItemGenerator(
     sidebarSlice: SidebarItem[],
   ): SidebarItemsGenerator {
-    return jest.fn(async () => sidebarSlice);
+    return jest.fn(() => sidebarSlice);
   }
 
   const StaticGeneratedSidebarSlice: NormalizedSidebar = [
@@ -40,7 +40,7 @@ describe('processSidebars', () => {
   // @ts-expect-error: good enough for this test
   const version: VersionMetadata = {
     versionName: '1.0.0',
-    versionPath: '/docs/1.0.0',
+    path: '/docs/1.0.0',
   };
 
   const params: SidebarProcessorParams = {
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/utils.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/utils.test.ts
index 7c2d4428c642..4085c9931dc7 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/utils.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/utils.test.ts
@@ -134,11 +134,11 @@ describe('createSidebarsUtils', () => {
     getFirstLink,
   } = createSidebarsUtils(sidebars);
 
-  it('getFirstDocIdOfFirstSidebar', async () => {
+  it('getFirstDocIdOfFirstSidebar', () => {
     expect(getFirstDocIdOfFirstSidebar()).toBe('doc1');
   });
 
-  it('getSidebarNameByDocId', async () => {
+  it('getSidebarNameByDocId', () => {
     expect(getSidebarNameByDocId('doc1')).toBe('sidebar1');
     expect(getSidebarNameByDocId('doc2')).toBe('sidebar1');
     expect(getSidebarNameByDocId('doc3')).toBe('sidebar2');
@@ -149,7 +149,7 @@ describe('createSidebarsUtils', () => {
     expect(getSidebarNameByDocId('unknown_id')).toBeUndefined();
   });
 
-  it('getDocNavigation', async () => {
+  it('getDocNavigation', () => {
     expect(getDocNavigation('doc1', 'doc1', undefined)).toEqual({
       sidebarName: 'sidebar1',
       previous: undefined,
@@ -229,7 +229,7 @@ describe('createSidebarsUtils', () => {
     });
   });
 
-  it('getCategoryGeneratedIndexNavigation', async () => {
+  it('getCategoryGeneratedIndexNavigation', () => {
     expect(
       getCategoryGeneratedIndexNavigation('/s3-subcategory-index-permalink'),
     ).toMatchObject({
@@ -259,7 +259,7 @@ describe('createSidebarsUtils', () => {
     });
   });
 
-  it('getCategoryGeneratedIndexList', async () => {
+  it('getCategoryGeneratedIndexList', () => {
     expect(getCategoryGeneratedIndexList()).toMatchObject([
       {
         type: 'category',
@@ -301,7 +301,7 @@ describe('createSidebarsUtils', () => {
 });
 
 describe('collectSidebarDocItems', () => {
-  it('can collect docs', async () => {
+  it('can collect docs', () => {
     const sidebar: Sidebar = [
       {
         type: 'category',
@@ -357,7 +357,7 @@ describe('collectSidebarDocItems', () => {
 });
 
 describe('collectSidebarCategories', () => {
-  it('can collect categories', async () => {
+  it('can collect categories', () => {
     const sidebar: Sidebar = [
       {
         type: 'category',
@@ -415,7 +415,7 @@ describe('collectSidebarCategories', () => {
 });
 
 describe('collectSidebarLinks', () => {
-  it('can collect links', async () => {
+  it('can collect links', () => {
     const sidebar: Sidebar = [
       {
         type: 'category',
@@ -453,7 +453,7 @@ describe('collectSidebarLinks', () => {
 });
 
 describe('collectSidebarsDocIds', () => {
-  it('can collect sidebars doc items', async () => {
+  it('can collect sidebars doc items', () => {
     const sidebar1: Sidebar = [
       {
         type: 'category',
@@ -499,7 +499,7 @@ describe('collectSidebarsDocIds', () => {
 });
 
 describe('transformSidebarItems', () => {
-  it('can transform sidebar items', async () => {
+  it('can transform sidebar items', () => {
     const sidebar: Sidebar = [
       {
         type: 'category',
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/validation.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/validation.test.ts
index d8f5fcab0d9e..8186601285a0 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/validation.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/validation.test.ts
@@ -9,7 +9,7 @@ import {validateSidebars, validateCategoryMetadataFile} from '../validation';
 import type {SidebarsConfig, CategoryMetadataFile} from '../types';
 
 describe('validateSidebars', () => {
-  it('throw for bad value', async () => {
+  it('throw for bad value', () => {
     expect(() => validateSidebars({sidebar: [{type: 42}]}))
       .toThrowErrorMatchingInlineSnapshot(`
       "{
@@ -21,12 +21,12 @@ describe('validateSidebars', () => {
     `);
   });
 
-  it('accept empty object', async () => {
+  it('accept empty object', () => {
     const sidebars: SidebarsConfig = {};
     validateSidebars(sidebars);
   });
 
-  it('accept valid values', async () => {
+  it('accept valid values', () => {
     const sidebars: SidebarsConfig = {
       sidebar1: [
         {type: 'doc', id: 'doc1'},
@@ -207,7 +207,7 @@ describe('validateSidebars', () => {
     ).toThrowErrorMatchingInlineSnapshot(`"sidebar.forEach is not a function"`);
   });
 
-  it('sidebars item doc but id is not a string', async () => {
+  it('sidebars item doc but id is not a string', () => {
     expect(() =>
       validateSidebars({
         docs: [
@@ -267,18 +267,18 @@ describe('validateSidebars', () => {
 describe('validateCategoryMetadataFile', () => {
   // TODO add more tests
 
-  it('throw for bad value', async () => {
+  it('throw for bad value', () => {
     expect(() =>
       validateCategoryMetadataFile(42),
     ).toThrowErrorMatchingInlineSnapshot(`""value" must be of type object"`);
   });
 
-  it('accept empty object', async () => {
+  it('accept empty object', () => {
     const content: CategoryMetadataFile = {};
     expect(validateCategoryMetadataFile(content)).toEqual(content);
   });
 
-  it('accept valid values', async () => {
+  it('accept valid values', () => {
     const content: CategoryMetadataFile = {
       className: 'className',
       label: 'Category Label',
@@ -295,7 +295,7 @@ describe('validateCategoryMetadataFile', () => {
     expect(validateCategoryMetadataFile(content)).toEqual(content);
   });
 
-  it('rejects permalink', async () => {
+  it('rejects permalink', () => {
     const content: CategoryMetadataFile = {
       className: 'className',
       label: 'Category Label',
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
index 56e0025a81af..7dc6ece7bedc 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
@@ -46,7 +46,7 @@ type Dir = {
 };
 
 // Comment for this feature: https://github.com/facebook/docusaurus/issues/3464#issuecomment-818670449
-export const DefaultSidebarItemsGenerator: SidebarItemsGenerator = async ({
+export const DefaultSidebarItemsGenerator: SidebarItemsGenerator = ({
   numberPrefixParser,
   isCategoryIndex,
   docs: allDocs,
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/postProcessor.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/postProcessor.ts
index 307ed9de8675..58c69912d704 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/postProcessor.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/postProcessor.ts
@@ -84,7 +84,7 @@ function postProcessSidebarItem(
       };
     }
     // A non-collapsible category can't be collapsed!
-    if (category.collapsible === false) {
+    if (!category.collapsible) {
       category.collapsed = false;
     }
     return category;
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
index 8284f09048ee..8d038f417537 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
@@ -251,7 +251,7 @@ export type SidebarItemsGeneratorArgs = {
 };
 export type SidebarItemsGenerator = (
   generatorArgs: SidebarItemsGeneratorArgs,
-) => Promise<NormalizedSidebar>;
+) => NormalizedSidebar | Promise<NormalizedSidebar>;
 
 export type SidebarItemsGeneratorOption = (
   generatorArgs: {
@@ -262,7 +262,7 @@ export type SidebarItemsGeneratorOption = (
      */
     defaultSidebarItemsGenerator: SidebarItemsGenerator;
   } & SidebarItemsGeneratorArgs,
-) => Promise<NormalizedSidebarItem[]>;
+) => NormalizedSidebar | Promise<NormalizedSidebar>;
 
 export type SidebarProcessorParams = {
   sidebarItemsGenerator: SidebarItemsGeneratorOption;
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/utils.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/utils.ts
index a213b2e7dedc..0c743f42d537 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/utils.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/utils.ts
@@ -257,7 +257,7 @@ export function createSidebarsUtils(sidebars: Sidebars): SidebarsUtils {
     ): boolean {
       return (
         item.type === 'category' &&
-        item.link?.type === 'generated-index' &&
+        item.link.type === 'generated-index' &&
         item.link.permalink === categoryGeneratedIndexPermalink
       );
     }
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/validation.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/validation.ts
index 22ddcfbf77ce..b9b1bfae007e 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/validation.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/validation.ts
@@ -144,7 +144,7 @@ function validateSidebarItem(
   // manually
   Joi.assert(item, sidebarItemSchema);
 
-  if ((item as NormalizedSidebarItemCategory).type === 'category') {
+  if ((item as NormalizedSidebarItem).type === 'category') {
     (item as NormalizedSidebarItemCategory).items.forEach(validateSidebarItem);
   }
 }
@@ -170,5 +170,9 @@ const categoryMetadataFileSchema = Joi.object<CategoryMetadataFile>({
 export function validateCategoryMetadataFile(
   unsafeContent: unknown,
 ): CategoryMetadataFile {
-  return Joi.attempt(unsafeContent, categoryMetadataFileSchema);
+  const {error, value} = categoryMetadataFileSchema.validate(unsafeContent);
+  if (error) {
+    throw error;
+  }
+  return value;
 }
diff --git a/packages/docusaurus-plugin-content-docs/src/slug.ts b/packages/docusaurus-plugin-content-docs/src/slug.ts
index 4815e210b01d..130c7a63b1f5 100644
--- a/packages/docusaurus-plugin-content-docs/src/slug.ts
+++ b/packages/docusaurus-plugin-content-docs/src/slug.ts
@@ -58,7 +58,7 @@ export default function getSlug({
     ) {
       return dirNameSlug;
     }
-    const baseSlug = frontMatterSlug || baseID;
+    const baseSlug = frontMatterSlug ?? baseID;
     return resolvePathname(baseSlug, getDirNameSlug());
   }
 
diff --git a/packages/docusaurus-plugin-content-docs/src/versions/__tests__/index.test.ts b/packages/docusaurus-plugin-content-docs/src/versions/__tests__/index.test.ts
index 4a3448460a24..773643ba8441 100644
--- a/packages/docusaurus-plugin-content-docs/src/versions/__tests__/index.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/versions/__tests__/index.test.ts
@@ -604,7 +604,7 @@ describe('readVersionsMetadata', () => {
           context: defaultContext,
         }),
       ).rejects.toThrowErrorMatchingInlineSnapshot(
-        `"Versions should be strings. Found type "number" for version "1.1"."`,
+        `"Versions should be strings. Found type "number" for version 1.1."`,
       );
       jsonMock.mockImplementationOnce(() => ['   ']);
 
diff --git a/packages/docusaurus-plugin-content-docs/src/versions/validation.ts b/packages/docusaurus-plugin-content-docs/src/versions/validation.ts
index 422d58f713d3..c2f1505275a0 100644
--- a/packages/docusaurus-plugin-content-docs/src/versions/validation.ts
+++ b/packages/docusaurus-plugin-content-docs/src/versions/validation.ts
@@ -11,7 +11,9 @@ import type {VersionsOptions} from '@docusaurus/plugin-content-docs';
 export function validateVersionName(name: unknown): asserts name is string {
   if (typeof name !== 'string') {
     throw new Error(
-      `Versions should be strings. Found type "${typeof name}" for version "${name}".`,
+      `Versions should be strings. Found type "${typeof name}" for version ${JSON.stringify(
+        name,
+      )}.`,
     );
   }
   if (!name.trim()) {
diff --git a/packages/docusaurus-plugin-content-pages/src/__tests__/index.test.ts b/packages/docusaurus-plugin-content-pages/src/__tests__/index.test.ts
index f3b94d2df5f4..31706d3a4cd4 100644
--- a/packages/docusaurus-plugin-content-pages/src/__tests__/index.test.ts
+++ b/packages/docusaurus-plugin-content-pages/src/__tests__/index.test.ts
@@ -16,7 +16,7 @@ describe('docusaurus-plugin-content-pages', () => {
   it('loads simple pages', async () => {
     const siteDir = path.join(__dirname, '__fixtures__', 'website');
     const context = await loadContext({siteDir});
-    const plugin = await pluginContentPages(
+    const plugin = pluginContentPages(
       context,
       validateOptions({
         validate: normalizePluginOptions,
@@ -33,7 +33,7 @@ describe('docusaurus-plugin-content-pages', () => {
   it('loads simple pages with french translations', async () => {
     const siteDir = path.join(__dirname, '__fixtures__', 'website');
     const context = await loadContext({siteDir});
-    const plugin = await pluginContentPages(
+    const plugin = pluginContentPages(
       {
         ...context,
         i18n: {
diff --git a/packages/docusaurus-plugin-content-pages/src/index.ts b/packages/docusaurus-plugin-content-pages/src/index.ts
index 66bcb0d15712..a9051e4545e6 100644
--- a/packages/docusaurus-plugin-content-pages/src/index.ts
+++ b/packages/docusaurus-plugin-content-pages/src/index.ts
@@ -39,10 +39,10 @@ export function getContentPathList(contentPaths: PagesContentPaths): string[] {
 const isMarkdownSource = (source: string) =>
   source.endsWith('.md') || source.endsWith('.mdx');
 
-export default async function pluginContentPages(
+export default function pluginContentPages(
   context: LoadContext,
   options: PluginOptions,
-): Promise<Plugin<LoadedContent | null>> {
+): Plugin<LoadedContent | null> {
   if (options.admonitions) {
     options.remarkPlugins = options.remarkPlugins.concat([
       [admonitions, options.admonitions],
diff --git a/packages/docusaurus-plugin-content-pages/src/markdownLoader.ts b/packages/docusaurus-plugin-content-pages/src/markdownLoader.ts
index e8ca79a21681..e5c91b7bf797 100644
--- a/packages/docusaurus-plugin-content-pages/src/markdownLoader.ts
+++ b/packages/docusaurus-plugin-content-pages/src/markdownLoader.ts
@@ -18,5 +18,5 @@ export default function markdownLoader(
   // TODO provide additional md processing here? like interlinking pages?
   // fileString = linkify(fileString)
 
-  return callback?.(null, fileString);
+  return callback(null, fileString);
 }
diff --git a/packages/docusaurus-plugin-content-pages/src/options.ts b/packages/docusaurus-plugin-content-pages/src/options.ts
index 475ed8311060..2c1f38201c30 100644
--- a/packages/docusaurus-plugin-content-pages/src/options.ts
+++ b/packages/docusaurus-plugin-content-pages/src/options.ts
@@ -28,7 +28,7 @@ export const DEFAULT_OPTIONS: PluginOptions = {
   admonitions: {},
 };
 
-const PluginOptionSchema = Joi.object({
+const PluginOptionSchema = Joi.object<PluginOptions>({
   path: Joi.string().default(DEFAULT_OPTIONS.path),
   routeBasePath: Joi.string().default(DEFAULT_OPTIONS.routeBasePath),
   include: Joi.array().items(Joi.string()).default(DEFAULT_OPTIONS.include),
diff --git a/packages/docusaurus-plugin-debug/src/theme/DebugSiteMetadata/index.tsx b/packages/docusaurus-plugin-debug/src/theme/DebugSiteMetadata/index.tsx
index 64d3954842c5..c366475762f8 100644
--- a/packages/docusaurus-plugin-debug/src/theme/DebugSiteMetadata/index.tsx
+++ b/packages/docusaurus-plugin-debug/src/theme/DebugSiteMetadata/index.tsx
@@ -20,7 +20,7 @@ export default function DebugMetadata(): JSX.Element {
       </div>
       <div>
         Site Version:{' '}
-        <code>{siteMetadata.siteVersion || 'No version specified'}</code>
+        <code>{siteMetadata.siteVersion ?? 'No version specified'}</code>
       </div>
       <h3 className={styles.sectionTitle}>Plugins and themes</h3>
       <ul className="clean-list">
diff --git a/packages/docusaurus-plugin-google-gtag/src/index.ts b/packages/docusaurus-plugin-google-gtag/src/index.ts
index 7724c9676683..2e278094e105 100644
--- a/packages/docusaurus-plugin-google-gtag/src/index.ts
+++ b/packages/docusaurus-plugin-google-gtag/src/index.ts
@@ -25,7 +25,7 @@ export default function pluginGoogleGtag(
   return {
     name: 'docusaurus-plugin-google-gtag',
 
-    async contentLoaded({actions}) {
+    contentLoaded({actions}) {
       actions.setGlobalData(options);
     },
 
diff --git a/packages/docusaurus-plugin-ideal-image/src/index.ts b/packages/docusaurus-plugin-ideal-image/src/index.ts
index d650e33b1006..4b8862171859 100644
--- a/packages/docusaurus-plugin-ideal-image/src/index.ts
+++ b/packages/docusaurus-plugin-ideal-image/src/index.ts
@@ -80,7 +80,7 @@ export function validateOptions({
   validate,
   options,
 }: OptionValidationContext<PluginOptions, PluginOptions>): PluginOptions {
-  const pluginOptionsSchema = Joi.object({
+  const pluginOptionsSchema = Joi.object<PluginOptions>({
     disableInDev: Joi.boolean().default(true),
   }).unknown();
   return validate(pluginOptionsSchema, options);
diff --git a/packages/docusaurus-plugin-ideal-image/src/theme/IdealImage/index.tsx b/packages/docusaurus-plugin-ideal-image/src/theme/IdealImage/index.tsx
index ff8ea85f6f2b..fbf2d3278a9b 100644
--- a/packages/docusaurus-plugin-ideal-image/src/theme/IdealImage/index.tsx
+++ b/packages/docusaurus-plugin-ideal-image/src/theme/IdealImage/index.tsx
@@ -22,9 +22,9 @@ function bytesToSize(bytes: number) {
   }
   const scale = Math.floor(Math.log(bytes) / Math.log(1024));
   if (scale === 0) {
-    return `${bytes} ${sizes[scale]}`;
+    return `${bytes} ${sizes[scale]!}`;
   }
-  return `${(bytes / 1024 ** scale).toFixed(1)} ${sizes[scale]}`;
+  return `${(bytes / 1024 ** scale).toFixed(1)} ${sizes[scale]!}`;
 }
 
 // Adopted from https://github.com/endiliey/react-ideal-image/blob/master/src/components/IdealImage/index.js#L43-L75
@@ -100,8 +100,8 @@ export default function IdealImage(props: Props): JSX.Element {
       {...props}
       alt={alt}
       className={className}
-      height={img.src.height || 100}
-      width={img.src.width || 100}
+      height={img.src.height ?? 100}
+      width={img.src.width ?? 100}
       placeholder={{lqip: img.preSrc}}
       src={img.src.src}
       srcSet={img.src.images.map((image) => ({
diff --git a/packages/docusaurus-plugin-pwa/src/index.ts b/packages/docusaurus-plugin-pwa/src/index.ts
index 7ec58b25f439..448e7d2f9917 100644
--- a/packages/docusaurus-plugin-pwa/src/index.ts
+++ b/packages/docusaurus-plugin-pwa/src/index.ts
@@ -89,7 +89,7 @@ export default function pluginPWA(
           new webpack.EnvironmentPlugin({
             PWA_DEBUG: debug,
             PWA_SERVICE_WORKER_URL: path.posix.resolve(
-              `${config.output?.publicPath || '/'}`,
+              `${(config.output?.publicPath as string) || '/'}`,
               'sw.js',
             ),
             PWA_OFFLINE_MODE_ACTIVATION_STRATEGIES:
@@ -102,7 +102,7 @@ export default function pluginPWA(
 
     injectHtmlTags() {
       const headTags: HtmlTags = [];
-      if (isProd && pwaHead) {
+      if (isProd) {
         pwaHead.forEach(({tagName, ...attributes}) => {
           (['href', 'content'] as const).forEach((attribute) => {
             const attributeValue = attributes[attribute];
@@ -160,7 +160,7 @@ export default function pluginPWA(
         plugins: [
           new webpack.EnvironmentPlugin({
             // Fallback value required with Webpack 5
-            PWA_SW_CUSTOM: swCustom || '',
+            PWA_SW_CUSTOM: swCustom ?? '',
           }),
           new LogPlugin({
             name: 'Service Worker',
@@ -189,7 +189,7 @@ export default function pluginPWA(
           '**/*.{png,jpg,jpeg,gif,svg,ico}',
           '**/*.{woff,woff2,eot,ttf,otf}',
           // @ts-expect-error: internal API?
-          ...(injectManifest.globPatterns ?? []),
+          ...((injectManifest.globPatterns as string[] | undefined) ?? []),
         ],
         // Those attributes are not overrideable
         swDest,
diff --git a/packages/docusaurus-plugin-pwa/src/options.ts b/packages/docusaurus-plugin-pwa/src/options.ts
index e96405756ad1..8517028f9f20 100644
--- a/packages/docusaurus-plugin-pwa/src/options.ts
+++ b/packages/docusaurus-plugin-pwa/src/options.ts
@@ -23,7 +23,7 @@ const DEFAULT_OPTIONS = {
   reloadPopup: '@theme/PwaReloadPopup',
 };
 
-const Schema = Joi.object({
+const optionsSchema = Joi.object<PluginOptions>({
   debug: Joi.bool().default(DEFAULT_OPTIONS.debug),
   offlineModeActivationStrategies: Joi.array()
     .items(
@@ -58,5 +58,5 @@ export function validateOptions({
   validate,
   options,
 }: OptionValidationContext<PluginOptions, PluginOptions>): PluginOptions {
-  return validate(Schema, options);
+  return validate(optionsSchema, options);
 }
diff --git a/packages/docusaurus-plugin-pwa/src/registerSw.ts b/packages/docusaurus-plugin-pwa/src/registerSw.ts
index 2bb7a92eb06b..d48e7b29b2f7 100644
--- a/packages/docusaurus-plugin-pwa/src/registerSw.ts
+++ b/packages/docusaurus-plugin-pwa/src/registerSw.ts
@@ -9,7 +9,7 @@ import {createStorageSlot} from '@docusaurus/theme-common';
 
 // First: read the env variables (provided by Webpack)
 /* eslint-disable prefer-destructuring */
-const PWA_SERVICE_WORKER_URL = process.env.PWA_SERVICE_WORKER_URL;
+const PWA_SERVICE_WORKER_URL = process.env.PWA_SERVICE_WORKER_URL!;
 const PWA_RELOAD_POPUP = process.env.PWA_RELOAD_POPUP;
 const PWA_OFFLINE_MODE_ACTIVATION_STRATEGIES = process.env
   .PWA_OFFLINE_MODE_ACTIVATION_STRATEGIES as unknown as (keyof typeof OfflineModeActivationStrategiesImplementations)[];
@@ -34,7 +34,7 @@ async function clearRegistrations() {
   }
   await Promise.all(
     registrations.map(async (registration) => {
-      const result = await registration?.unregister();
+      const result = await registration.unregister();
       if (debug) {
         console.log(
           `[Docusaurus-PWA][registerSw]: unregister() service worker registration`,
@@ -69,7 +69,7 @@ async function isAppInstalledEventFired() {
 declare global {
   interface Navigator {
     getInstalledRelatedApps: () => Promise<{platform: string}[]>;
-    connection: {effectiveType: string; saveData: boolean};
+    connection?: {effectiveType: string; saveData: boolean};
   }
 }
 
diff --git a/packages/docusaurus-plugin-sitemap/src/options.ts b/packages/docusaurus-plugin-sitemap/src/options.ts
index 5a8302424e83..365f60156eaf 100644
--- a/packages/docusaurus-plugin-sitemap/src/options.ts
+++ b/packages/docusaurus-plugin-sitemap/src/options.ts
@@ -29,7 +29,8 @@ export const DEFAULT_OPTIONS: PluginOptions = {
   ignorePatterns: [],
 };
 
-const PluginOptionSchema = Joi.object({
+const PluginOptionSchema = Joi.object<PluginOptions>({
+  // @ts-expect-error: forbidden
   cacheTime: Joi.forbidden().messages({
     'any.unknown':
       'Option `cacheTime` in sitemap config is deprecated. Please remove it.',
diff --git a/packages/docusaurus-remark-plugin-npm2yarn/src/index.ts b/packages/docusaurus-remark-plugin-npm2yarn/src/index.ts
index 28b4c7e89150..39236a1537b4 100644
--- a/packages/docusaurus-remark-plugin-npm2yarn/src/index.ts
+++ b/packages/docusaurus-remark-plugin-npm2yarn/src/index.ts
@@ -62,8 +62,8 @@ const nodeForImport: Literal = {
 const plugin: Plugin<[PluginOptions?]> = (options = {}) => {
   const {sync = false} = options;
   return (root) => {
-    let transformed = false;
-    let alreadyImported = false;
+    let transformed = false as boolean;
+    let alreadyImported = false as boolean;
     visit(root, (node: Node) => {
       if (isImport(node) && node.value.includes('@theme/Tabs')) {
         alreadyImported = true;
diff --git a/packages/docusaurus-theme-classic/src/index.ts b/packages/docusaurus-theme-classic/src/index.ts
index a0cb4629cb58..c87fef7f4b7e 100644
--- a/packages/docusaurus-theme-classic/src/index.ts
+++ b/packages/docusaurus-theme-classic/src/index.ts
@@ -177,7 +177,7 @@ export default function themeClassic(
         const plugin: PostCssPlugin = {
           postcssPlugin: 'RtlCssPlugin',
           prepare: (result) => {
-            const file = result.root?.source?.input?.file;
+            const file = result.root.source?.input.file;
             // Skip Infima as we are using the its RTL version.
             if (file === resolvedInfimaFile) {
               return {};
diff --git a/packages/docusaurus-theme-classic/src/theme-classic.d.ts b/packages/docusaurus-theme-classic/src/theme-classic.d.ts
index ef8c33023fd2..4aa679bd4946 100644
--- a/packages/docusaurus-theme-classic/src/theme-classic.d.ts
+++ b/packages/docusaurus-theme-classic/src/theme-classic.d.ts
@@ -21,12 +21,14 @@
 // in their tsconfig.
 
 declare module '@docusaurus/theme-classic' {
-  import type {LoadContext, Plugin} from '@docusaurus/types';
+  import type {LoadContext, Plugin, PluginModule} from '@docusaurus/types';
 
   export type Options = {
     customCss?: string | string[];
   };
 
+  export const getSwizzleConfig: PluginModule['getSwizzleConfig'];
+
   export default function themeClassic(
     context: LoadContext,
     options: Options,
diff --git a/packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/String.tsx b/packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/String.tsx
index 5a9384f7b638..9947164ddbef 100644
--- a/packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/String.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/String.tsx
@@ -52,7 +52,7 @@ export default function CodeBlockString({
     magicComments,
   });
   const showLineNumbers =
-    showLineNumbersProp || containsLineNumbers(metastring);
+    showLineNumbersProp ?? containsLineNumbers(metastring);
 
   return (
     <Container
diff --git a/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Html/index.tsx b/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Html/index.tsx
index 7f6bab8f6cc6..a7413b0d7154 100644
--- a/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Html/index.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Html/index.tsx
@@ -23,7 +23,7 @@ export default function DocSidebarItemHtml({
       className={clsx(
         ThemeClassNames.docs.docSidebarItemLink,
         ThemeClassNames.docs.docSidebarItemLinkLevel(level),
-        defaultStyle && `${styles.menuHtmlItem} menu__list-item`,
+        defaultStyle && [styles.menuHtmlItem, 'menu__list-item'],
         className,
       )}
       key={index}
diff --git a/packages/docusaurus-theme-classic/src/theme/Footer/Links/MultiColumn/index.tsx b/packages/docusaurus-theme-classic/src/theme/Footer/Links/MultiColumn/index.tsx
index 01b362e520c0..2239e8c8fb66 100644
--- a/packages/docusaurus-theme-classic/src/theme/Footer/Links/MultiColumn/index.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/Footer/Links/MultiColumn/index.tsx
@@ -21,7 +21,7 @@ function ColumnLinkItem({item}: {item: ColumnItemType}) {
       dangerouslySetInnerHTML={{__html: item.html}}
     />
   ) : (
-    <li key={item.href || item.to} className="footer__item">
+    <li key={item.href ?? item.to} className="footer__item">
       <LinkItem item={item} />
     </li>
   );
diff --git a/packages/docusaurus-theme-common/src/components/Collapsible/index.tsx b/packages/docusaurus-theme-common/src/components/Collapsible/index.tsx
index b6210a2b3660..39c6ce63fdf1 100644
--- a/packages/docusaurus-theme-common/src/components/Collapsible/index.tsx
+++ b/packages/docusaurus-theme-common/src/components/Collapsible/index.tsx
@@ -27,7 +27,7 @@ export function useCollapsible({
   initialState,
 }: {
   /** The initial state. Will be non-collapsed by default. */
-  initialState: boolean | (() => boolean);
+  initialState?: boolean | (() => boolean);
 }): {
   collapsed: boolean;
   setCollapsed: Dispatch<SetStateAction<boolean>>;
diff --git a/packages/docusaurus-theme-common/src/hooks/useSkipToContent.ts b/packages/docusaurus-theme-common/src/hooks/useSkipToContent.ts
index 54e6a42f3a85..bdcac465d487 100644
--- a/packages/docusaurus-theme-common/src/hooks/useSkipToContent.ts
+++ b/packages/docusaurus-theme-common/src/hooks/useSkipToContent.ts
@@ -40,7 +40,7 @@ export function useSkipToContent(): {
     e.preventDefault();
 
     const targetElement: HTMLElement | null =
-      document.querySelector('main:first-of-type') ||
+      document.querySelector('main:first-of-type') ??
       document.querySelector(`.${ThemeClassNames.wrapper.main}`);
 
     if (targetElement) {
diff --git a/packages/docusaurus-theme-common/src/hooks/useTOCHighlight.ts b/packages/docusaurus-theme-common/src/hooks/useTOCHighlight.ts
index fca0174fe644..924ede9e09c3 100644
--- a/packages/docusaurus-theme-common/src/hooks/useTOCHighlight.ts
+++ b/packages/docusaurus-theme-common/src/hooks/useTOCHighlight.ts
@@ -38,15 +38,12 @@ function getAnchors({
 }: {
   minHeadingLevel: number;
   maxHeadingLevel: number;
-}) {
+}): HTMLElement[] {
   const selectors = [];
   for (let i = minHeadingLevel; i <= maxHeadingLevel; i += 1) {
     selectors.push(`h${i}.anchor`);
   }
-
-  return Array.from(
-    document.querySelectorAll(selectors.join()),
-  ) as HTMLElement[];
+  return Array.from(document.querySelectorAll(selectors.join()));
 }
 
 function getActiveAnchor(
diff --git a/packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts b/packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts
index 97c9056eb297..a0d3163df88e 100644
--- a/packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts
@@ -171,7 +171,7 @@ export function parseLines(
     const metastringRangeClassName = magicComments[0]!.className;
     const lines = rangeParser(linesRange)
       .filter((n) => n > 0)
-      .map((n) => [n - 1, [metastringRangeClassName]]);
+      .map((n) => [n - 1, [metastringRangeClassName]] as [number, string[]]);
     return {lineClassNames: Object.fromEntries(lines), code};
   }
   if (language === undefined) {
@@ -189,7 +189,7 @@ export function parseLines(
   const lineToClassName: {[comment: string]: string} = Object.fromEntries(
     magicComments
       .filter((d) => d.line)
-      .map(({className, line}) => [line, className]),
+      .map(({className, line}) => [line!, className] as [string, string]),
   );
   const blockStartToClassName: {[comment: string]: string} = Object.fromEntries(
     magicComments
diff --git a/packages/docusaurus-theme-common/src/utils/reactUtils.tsx b/packages/docusaurus-theme-common/src/utils/reactUtils.tsx
index 09cb1b7b52e7..4a7410e3fb6d 100644
--- a/packages/docusaurus-theme-common/src/utils/reactUtils.tsx
+++ b/packages/docusaurus-theme-common/src/utils/reactUtils.tsx
@@ -70,7 +70,7 @@ export class ReactContextError extends Error {
     this.name = 'ReactContextError';
     this.message = `Hook ${
       this.stack?.split('\n')[1]?.match(/at (?:\w+\.)?(?<name>\w+)/)?.groups!
-        .name
+        .name ?? ''
     } is called outside the <${providerName}>. ${additionalInfo || ''}`;
   }
 }
diff --git a/packages/docusaurus-theme-common/src/utils/routesUtils.ts b/packages/docusaurus-theme-common/src/utils/routesUtils.ts
index 4faa24b675a0..b662ab4bf23d 100644
--- a/packages/docusaurus-theme-common/src/utils/routesUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/routesUtils.ts
@@ -18,7 +18,7 @@ export function isSamePath(
   path2: string | undefined,
 ): boolean {
   const normalize = (pathname: string | undefined) =>
-    (!pathname || pathname?.endsWith('/')
+    (!pathname || pathname.endsWith('/')
       ? pathname
       : `${pathname}/`
     )?.toLowerCase();
diff --git a/packages/docusaurus-theme-common/src/utils/scrollUtils.tsx b/packages/docusaurus-theme-common/src/utils/scrollUtils.tsx
index 32095c3feac3..514222d18ac0 100644
--- a/packages/docusaurus-theme-common/src/utils/scrollUtils.tsx
+++ b/packages/docusaurus-theme-common/src/utils/scrollUtils.tsx
@@ -112,11 +112,7 @@ export function useScrollPosition(
         return;
       }
       const currentPosition = getScrollPosition()!;
-
-      if (dynamicEffect) {
-        dynamicEffect(currentPosition, lastPositionRef.current);
-      }
-
+      dynamicEffect(currentPosition, lastPositionRef.current);
       lastPositionRef.current = currentPosition;
     };
 
diff --git a/packages/docusaurus-theme-common/src/utils/searchUtils.ts b/packages/docusaurus-theme-common/src/utils/searchUtils.ts
index 7f6fe91e48f0..082f0fb7085c 100644
--- a/packages/docusaurus-theme-common/src/utils/searchUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/searchUtils.ts
@@ -39,7 +39,7 @@ export function useContextualSearchFilters(): {locale: string; tags: string[]} {
   // plugin instances.
   function getDocPluginTags(pluginId: string) {
     const activeVersion =
-      activePluginAndVersion?.activePlugin?.pluginId === pluginId
+      activePluginAndVersion?.activePlugin.pluginId === pluginId
         ? activePluginAndVersion.activeVersion
         : undefined;
 
diff --git a/packages/docusaurus-theme-common/src/utils/tocUtils.ts b/packages/docusaurus-theme-common/src/utils/tocUtils.ts
index 8f12d780719d..64be4cb51191 100644
--- a/packages/docusaurus-theme-common/src/utils/tocUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/tocUtils.ts
@@ -27,7 +27,7 @@ function treeifyTOC(flatTOC: readonly TOCItem[]): TOCTreeNode[] {
   // level <i>. We will modify these indices as we iterate through all headings.
   // e.g. if an ### H3 was last seen at index 2, then prevIndexForLevel[3] === 2
   // indices 0 and 1 will remain unused.
-  const prevIndexForLevel = Array(7).fill(-1);
+  const prevIndexForLevel = Array<number>(7).fill(-1);
 
   headings.forEach((curr, currIndex) => {
     // Take the last seen index for each ancestor level. the highest index will
diff --git a/packages/docusaurus-theme-common/src/utils/usePluralForm.ts b/packages/docusaurus-theme-common/src/utils/usePluralForm.ts
index cc5ce45317bf..726d406db2d7 100644
--- a/packages/docusaurus-theme-common/src/utils/usePluralForm.ts
+++ b/packages/docusaurus-theme-common/src/utils/usePluralForm.ts
@@ -95,7 +95,11 @@ function selectPluralMessage(
   }
   if (parts.length > localePluralForms.pluralForms.length) {
     console.error(
-      `For locale=${localePluralForms.locale}, a maximum of ${localePluralForms.pluralForms.length} plural forms are expected (${localePluralForms.pluralForms}), but the message contains ${parts.length}: ${pluralMessages}`,
+      `For locale=${localePluralForms.locale}, a maximum of ${
+        localePluralForms.pluralForms.length
+      } plural forms are expected (${localePluralForms.pluralForms.join(
+        ',',
+      )}), but the message contains ${parts.length}: ${pluralMessages}`,
     );
   }
   const pluralForm = localePluralForms.select(count);
diff --git a/packages/docusaurus-theme-live-codeblock/src/validateThemeConfig.ts b/packages/docusaurus-theme-live-codeblock/src/validateThemeConfig.ts
index 4b9fb583be03..d642214987de 100644
--- a/packages/docusaurus-theme-live-codeblock/src/validateThemeConfig.ts
+++ b/packages/docusaurus-theme-live-codeblock/src/validateThemeConfig.ts
@@ -15,7 +15,7 @@ export const DEFAULT_CONFIG = {
   playgroundPosition: 'bottom',
 };
 
-export const Schema = Joi.object({
+export const Schema = Joi.object<ThemeConfig>({
   liveCodeBlock: Joi.object({
     playgroundPosition: Joi.string()
       .equal('top', 'bottom')
diff --git a/packages/docusaurus-theme-search-algolia/src/index.ts b/packages/docusaurus-theme-search-algolia/src/index.ts
index dbd2a58db30c..af54aafba33f 100644
--- a/packages/docusaurus-theme-search-algolia/src/index.ts
+++ b/packages/docusaurus-theme-search-algolia/src/index.ts
@@ -60,7 +60,7 @@ export default function themeSearchAlgolia(context: LoadContext): Plugin<void> {
       });
     },
 
-    async contentLoaded({actions: {addRoute}}) {
+    contentLoaded({actions: {addRoute}}) {
       if (searchPagePath) {
         addRoute({
           path: normalizeUrl([baseUrl, searchPagePath]),
diff --git a/packages/docusaurus-theme-search-algolia/src/validateThemeConfig.ts b/packages/docusaurus-theme-search-algolia/src/validateThemeConfig.ts
index 68bd60d163a1..a2a2ccd7869e 100644
--- a/packages/docusaurus-theme-search-algolia/src/validateThemeConfig.ts
+++ b/packages/docusaurus-theme-search-algolia/src/validateThemeConfig.ts
@@ -20,7 +20,7 @@ export const DEFAULT_CONFIG = {
   searchPagePath: 'search',
 };
 
-export const Schema = Joi.object({
+export const Schema = Joi.object<ThemeConfig>({
   algolia: Joi.object({
     // Docusaurus attributes
     contextualSearch: Joi.boolean().default(DEFAULT_CONFIG.contextualSearch),
diff --git a/packages/docusaurus-theme-translations/src/index.ts b/packages/docusaurus-theme-translations/src/index.ts
index f6b7e7303e19..8b9afb841d90 100644
--- a/packages/docusaurus-theme-translations/src/index.ts
+++ b/packages/docusaurus-theme-translations/src/index.ts
@@ -25,9 +25,9 @@ export function codeTranslationLocalesToTry(locale: string): string[] {
     // unresolved except for simply locales
     locale,
     // "zh-CN" / "pt-BR"
-    `${maximizedLocale.language}-${maximizedLocale.region}`,
+    `${maximizedLocale.language!}-${maximizedLocale.region!}`,
     // "zh-Hans" / "pt-Latn"
-    `${maximizedLocale.language}-${maximizedLocale.script}`,
+    `${maximizedLocale.language!}-${maximizedLocale.script!}`,
     // "zh" / "pt"
     maximizedLocale.language!,
   ];
diff --git a/packages/docusaurus-utils-validation/src/JoiFrontMatter.ts b/packages/docusaurus-utils-validation/src/JoiFrontMatter.ts
index b09f528ec14d..5de48285cc38 100644
--- a/packages/docusaurus-utils-validation/src/JoiFrontMatter.ts
+++ b/packages/docusaurus-utils-validation/src/JoiFrontMatter.ts
@@ -28,4 +28,4 @@ const JoiFrontMatterString: Joi.Extension = {
  * @see https://github.com/facebook/docusaurus/issues/4642
  * @see https://github.com/sideway/joi/issues/1442#issuecomment-823997884
  */
-export const JoiFrontMatter: typeof Joi = Joi.extend(JoiFrontMatterString);
+export const JoiFrontMatter = Joi.extend(JoiFrontMatterString) as typeof Joi;
diff --git a/packages/docusaurus-utils/src/pathUtils.ts b/packages/docusaurus-utils/src/pathUtils.ts
index a9fbb0bd98f7..35b8bd2656e8 100644
--- a/packages/docusaurus-utils/src/pathUtils.ts
+++ b/packages/docusaurus-utils/src/pathUtils.ts
@@ -56,7 +56,7 @@ export function shortName(str: string): string {
  * Adopted from https://github.com/sindresorhus/slash/blob/main/index.js
  */
 export function posixPath(str: string): string {
-  const isExtendedLengthPath = /^\\\\\?\\/.test(str);
+  const isExtendedLengthPath = str.startsWith('\\\\?\\');
 
   // Forward slashes are only valid Windows paths when they don't contain non-
   // ascii characters.
diff --git a/packages/docusaurus-utils/src/urlUtils.ts b/packages/docusaurus-utils/src/urlUtils.ts
index 708d50dbfe57..06694a00bd09 100644
--- a/packages/docusaurus-utils/src/urlUtils.ts
+++ b/packages/docusaurus-utils/src/urlUtils.ts
@@ -72,11 +72,11 @@ export function normalizeUrl(rawUrls: string[]): string {
           /^\/+/,
           // Special case where the first element of rawUrls is empty
           // ["", "/hello"] => /hello
-          component[0] === '/' && !hasStartingSlash ? '/' : '',
+          component.startsWith('/') && !hasStartingSlash ? '/' : '',
         );
       }
 
-      hasEndingSlash = component[component.length - 1] === '/';
+      hasEndingSlash = component.endsWith('/');
       // Removing the ending slashes for each component but the last. For the
       // last component we will combine multiple slashes to a single one.
       component = component.replace(/\/+$/, i < urls.length - 1 ? '' : '/');
@@ -95,7 +95,7 @@ export function normalizeUrl(rawUrls: string[]): string {
 
   // Replace ? in parameters with &.
   const parts = str.split('?');
-  str = parts.shift() + (parts.length > 0 ? '?' : '') + parts.join('&');
+  str = parts.shift()! + (parts.length > 0 ? '?' : '') + parts.join('&');
 
   // Dedupe forward slashes in the entire path, avoiding protocol slashes.
   str = str.replace(/(?<textBefore>[^:/]\/)\/+/g, '$1');
diff --git a/packages/docusaurus/src/client/docusaurus.ts b/packages/docusaurus/src/client/docusaurus.ts
index 80fa879e30cb..987f931ede0a 100644
--- a/packages/docusaurus/src/client/docusaurus.ts
+++ b/packages/docusaurus/src/client/docusaurus.ts
@@ -19,7 +19,7 @@ declare global {
   // eslint-disable-next-line camelcase, no-underscore-dangle
   const __webpack_require__: {gca: (name: string) => string};
   interface Navigator {
-    connection: {effectiveType: string; saveData: boolean};
+    connection?: {effectiveType: string; saveData: boolean};
   }
 }
 
diff --git a/packages/docusaurus/src/client/exports/useBaseUrl.ts b/packages/docusaurus/src/client/exports/useBaseUrl.ts
index 174ea539c1b7..c5481e57670f 100644
--- a/packages/docusaurus/src/client/exports/useBaseUrl.ts
+++ b/packages/docusaurus/src/client/exports/useBaseUrl.ts
@@ -10,7 +10,7 @@ import {hasProtocol} from './isInternalUrl';
 import type {BaseUrlOptions, BaseUrlUtils} from '@docusaurus/useBaseUrl';
 
 function addBaseUrl(
-  siteUrl: string | undefined,
+  siteUrl: string,
   baseUrl: string,
   url: string,
   {forcePrependBaseUrl = false, absolute = false}: BaseUrlOptions = {},
diff --git a/packages/docusaurus/src/commands/serve.ts b/packages/docusaurus/src/commands/serve.ts
index da94dc86678d..64845cb5ced4 100644
--- a/packages/docusaurus/src/commands/serve.ts
+++ b/packages/docusaurus/src/commands/serve.ts
@@ -66,7 +66,7 @@ export async function serve(
 
     // Remove baseUrl before calling serveHandler, because /baseUrl/ should
     // serve /build/index.html, not /build/baseUrl/index.html (does not exist)
-    req.url = req.url?.replace(baseUrl, '/');
+    req.url = req.url.replace(baseUrl, '/');
 
     serveHandler(req, res, {
       cleanUrls: true,
diff --git a/packages/docusaurus/src/commands/swizzle/__tests__/config.test.ts b/packages/docusaurus/src/commands/swizzle/__tests__/config.test.ts
index cb924a626ffc..8042d3d51dae 100644
--- a/packages/docusaurus/src/commands/swizzle/__tests__/config.test.ts
+++ b/packages/docusaurus/src/commands/swizzle/__tests__/config.test.ts
@@ -9,14 +9,14 @@ import {normalizeSwizzleConfig} from '../config';
 import type {SwizzleConfig} from '@docusaurus/types';
 
 describe('normalizeSwizzleConfig', () => {
-  it(`validate no components config`, async () => {
+  it(`validate no components config`, () => {
     const config: SwizzleConfig = {
       components: {},
     };
     expect(normalizeSwizzleConfig(config)).toEqual(config);
   });
 
-  it(`validate complete config`, async () => {
+  it(`validate complete config`, () => {
     const config: SwizzleConfig = {
       components: {
         SomeComponent: {
@@ -38,7 +38,7 @@ describe('normalizeSwizzleConfig', () => {
     expect(normalizeSwizzleConfig(config)).toEqual(config);
   });
 
-  it(`normalize partial config`, async () => {
+  it(`normalize partial config`, () => {
     const config: SwizzleConfig = {
       components: {
         SomeComponent: {
@@ -59,7 +59,7 @@ describe('normalizeSwizzleConfig', () => {
     expect(normalizeSwizzleConfig(config)).toMatchSnapshot();
   });
 
-  it(`reject missing components`, async () => {
+  it(`reject missing components`, () => {
     // @ts-expect-error: incomplete actions map
     const config: SwizzleConfig = {};
 
@@ -70,7 +70,7 @@ describe('normalizeSwizzleConfig', () => {
     );
   });
 
-  it(`reject invalid action name`, async () => {
+  it(`reject invalid action name`, () => {
     const config: SwizzleConfig = {
       components: {
         MyComponent: {
@@ -91,7 +91,7 @@ describe('normalizeSwizzleConfig', () => {
     );
   });
 
-  it(`reject invalid action status`, async () => {
+  it(`reject invalid action status`, () => {
     const config: SwizzleConfig = {
       components: {
         MyComponent: {
diff --git a/packages/docusaurus/src/commands/swizzle/actions.ts b/packages/docusaurus/src/commands/swizzle/actions.ts
index e295f8c2bd2d..44aba75cca13 100644
--- a/packages/docusaurus/src/commands/swizzle/actions.ts
+++ b/packages/docusaurus/src/commands/swizzle/actions.ts
@@ -109,7 +109,7 @@ export async function wrap({
   const isDirectory = await isDir(path.join(themePath, themeComponentName));
 
   // Top/Parent/ComponentName => ComponentName
-  const componentName = _.last(themeComponentName.split('/'));
+  const componentName = _.last(themeComponentName.split('/'))!;
   const wrapperComponentName = `${componentName}Wrapper`;
 
   const wrapperFileName = `${themeComponentName}${isDirectory ? '/index' : ''}${
diff --git a/packages/docusaurus/src/commands/swizzle/config.ts b/packages/docusaurus/src/commands/swizzle/config.ts
index 83f0bbe75101..b72f30cc60c9 100644
--- a/packages/docusaurus/src/commands/swizzle/config.ts
+++ b/packages/docusaurus/src/commands/swizzle/config.ts
@@ -16,9 +16,8 @@ function getModuleSwizzleConfig(
   swizzlePlugin: SwizzlePlugin,
 ): SwizzleConfig | undefined {
   const getSwizzleConfig =
-    swizzlePlugin.plugin.plugin?.getSwizzleConfig ??
-    swizzlePlugin.plugin.pluginModule?.module.getSwizzleConfig ??
-    swizzlePlugin.plugin.pluginModule?.module?.getSwizzleConfig;
+    swizzlePlugin.plugin.plugin.getSwizzleConfig ??
+    swizzlePlugin.plugin.pluginModule?.module.getSwizzleConfig;
 
   if (getSwizzleConfig) {
     return getSwizzleConfig();
@@ -26,9 +25,8 @@ function getModuleSwizzleConfig(
 
   // TODO deprecate getSwizzleComponentList later
   const getSwizzleComponentList =
-    swizzlePlugin.plugin.plugin?.getSwizzleComponentList ??
-    swizzlePlugin.plugin.pluginModule?.module.getSwizzleComponentList ??
-    swizzlePlugin.plugin.pluginModule?.module?.getSwizzleComponentList;
+    swizzlePlugin.plugin.plugin.getSwizzleComponentList ??
+    swizzlePlugin.plugin.pluginModule?.module.getSwizzleComponentList;
 
   if (getSwizzleComponentList) {
     const safeComponents = getSwizzleComponentList() ?? [];
diff --git a/packages/docusaurus/src/commands/swizzle/themes.ts b/packages/docusaurus/src/commands/swizzle/themes.ts
index c31b0f28dd8b..84961dd9716c 100644
--- a/packages/docusaurus/src/commands/swizzle/themes.ts
+++ b/packages/docusaurus/src/commands/swizzle/themes.ts
@@ -15,7 +15,7 @@ import {findStringIgnoringCase, type SwizzlePlugin} from './common';
 export function pluginToThemeName(plugin: SwizzlePlugin): string | undefined {
   if (plugin.instance.getThemePath) {
     return (
-      (plugin.instance.version as {name: string}).name ?? plugin.instance.name
+      (plugin.instance.version as {name?: string}).name ?? plugin.instance.name
     );
   }
   return undefined;
@@ -76,9 +76,7 @@ function handleInvalidThemeName({
   // TODO recover from short theme-names here: "classic" => "@docusaurus/theme-classic"
 
   // No recovery value is possible: print error
-  const suggestion = themeNames.find(
-    (name) => leven(name, themeNameParam!) < 4,
-  );
+  const suggestion = themeNames.find((name) => leven(name, themeNameParam) < 4);
   logger.error`Theme name=${themeNameParam} not found. ${
     suggestion
       ? logger.interpolate`Did you mean name=${suggestion}?`
@@ -87,13 +85,13 @@ function handleInvalidThemeName({
   return process.exit(1);
 }
 
-async function validateThemeName({
+function validateThemeName({
   themeNameParam,
   themeNames,
 }: {
   themeNameParam: string;
   themeNames: string[];
-}): Promise<string> {
+}): string {
   const isValidName = themeNames.includes(themeNameParam);
   if (!isValidName) {
     return handleInvalidThemeName({
diff --git a/packages/docusaurus/src/commands/writeHeadingIds.ts b/packages/docusaurus/src/commands/writeHeadingIds.ts
index fe15c0b1f3ef..73bc699c25b3 100644
--- a/packages/docusaurus/src/commands/writeHeadingIds.ts
+++ b/packages/docusaurus/src/commands/writeHeadingIds.ts
@@ -37,12 +37,12 @@ async function transformMarkdownFile(
 async function getPathsToWatch(siteDir: string): Promise<string[]> {
   const context = await loadContext({siteDir});
   const plugins = await initPlugins(context);
-  return plugins.flatMap((plugin) => plugin?.getPathsToWatch?.() ?? []);
+  return plugins.flatMap((plugin) => plugin.getPathsToWatch?.() ?? []);
 }
 
 export async function writeHeadingIds(
   siteDir: string,
-  files: string[],
+  files: string[] | undefined,
   options: WriteHeadingIDOptions,
 ): Promise<void> {
   const markdownFiles = await safeGlobby(
diff --git a/packages/docusaurus/src/deps.d.ts b/packages/docusaurus/src/deps.d.ts
index 06f478ca6330..57de485ea0ce 100644
--- a/packages/docusaurus/src/deps.d.ts
+++ b/packages/docusaurus/src/deps.d.ts
@@ -20,13 +20,13 @@ declare module 'react-loadable-ssr-addon-v5-slorber' {
   export type Manifest = {
     entrypoints: string[];
     origins: {[key: string]: number[]};
-    assets: Array<{[key: string]: Asset[]}>;
+    assets: {[key: string]: Asset[]}[];
   };
 
   export function getBundles(
     manifest: Manifest,
     modulesToBeLoaded: string[],
-  ): {js: Asset[]; css: Asset[]};
+  ): {js?: Asset[]; css?: Asset[]};
 
   export default class ReactLoadableSSRAddon implements WebpackPluginInstance {
     constructor(props: {filename: string});
diff --git a/packages/docusaurus/src/server/plugins/configs.ts b/packages/docusaurus/src/server/plugins/configs.ts
index b7b7bbf6ccd4..eb2898e5d312 100644
--- a/packages/docusaurus/src/server/plugins/configs.ts
+++ b/packages/docusaurus/src/server/plugins/configs.ts
@@ -63,7 +63,7 @@ async function normalizePluginConfig(
     const pluginPath = pluginRequire.resolve(pluginModuleImport);
     const pluginModule = importFresh<ImportedPluginModule>(pluginPath);
     return {
-      plugin: pluginModule?.default ?? pluginModule,
+      plugin: pluginModule.default ?? pluginModule,
       options: {},
       pluginModule: {
         path: pluginModuleImport,
@@ -90,7 +90,7 @@ async function normalizePluginConfig(
     const pluginPath = pluginRequire.resolve(pluginModuleImport);
     const pluginModule = importFresh<ImportedPluginModule>(pluginPath);
     return {
-      plugin: pluginModule?.default ?? pluginModule,
+      plugin: pluginModule.default ?? pluginModule,
       options: pluginConfig[1],
       pluginModule: {
         path: pluginModuleImport,
diff --git a/packages/docusaurus/src/server/plugins/index.ts b/packages/docusaurus/src/server/plugins/index.ts
index 812ea7b2e80e..5a8dbb98d095 100644
--- a/packages/docusaurus/src/server/plugins/index.ts
+++ b/packages/docusaurus/src/server/plugins/index.ts
@@ -52,7 +52,7 @@ export async function loadPlugins(context: LoadContext): Promise<{
     plugins.map(async (plugin) => {
       const content = await plugin.loadContent?.();
       const rawTranslationFiles =
-        (await plugin?.getTranslationFiles?.({content})) ?? [];
+        (await plugin.getTranslationFiles?.({content})) ?? [];
       const translationFiles = await Promise.all(
         rawTranslationFiles.map((translationFile) =>
           localizePluginTranslationFile({
diff --git a/packages/docusaurus/src/server/plugins/init.ts b/packages/docusaurus/src/server/plugins/init.ts
index 771a407cccb5..c19f82d15b80 100644
--- a/packages/docusaurus/src/server/plugins/init.ts
+++ b/packages/docusaurus/src/server/plugins/init.ts
@@ -29,8 +29,8 @@ function getOptionValidationFunction(
   if (normalizedPluginConfig.pluginModule) {
     // Support both CommonJS and ES modules
     return (
-      normalizedPluginConfig.pluginModule.module?.default?.validateOptions ??
-      normalizedPluginConfig.pluginModule.module?.validateOptions
+      normalizedPluginConfig.pluginModule.module.default?.validateOptions ??
+      normalizedPluginConfig.pluginModule.module.validateOptions
     );
   }
   return normalizedPluginConfig.plugin.validateOptions;
@@ -66,7 +66,7 @@ export async function initPlugins(
   ): Promise<PluginVersionInformation> {
     if (normalizedPluginConfig.pluginModule?.path) {
       const pluginPath = pluginRequire.resolve(
-        normalizedPluginConfig.pluginModule?.path,
+        normalizedPluginConfig.pluginModule.path,
       );
       return getPluginVersion(pluginPath, context.siteDir);
     }
diff --git a/packages/docusaurus/src/server/plugins/moduleShorthand.ts b/packages/docusaurus/src/server/plugins/moduleShorthand.ts
index df0ab5570d43..5a106e88fe30 100644
--- a/packages/docusaurus/src/server/plugins/moduleShorthand.ts
+++ b/packages/docusaurus/src/server/plugins/moduleShorthand.ts
@@ -14,7 +14,10 @@ export function getNamePatterns(
     if (!moduleName.includes('/')) {
       return [`${moduleName}/docusaurus-${moduleType}`];
     }
-    const [scope, packageName] = moduleName.split(/\/(?<rest>.*)/);
+    const [scope, packageName] = moduleName.split(/\/(?<rest>.*)/) as [
+      string,
+      string,
+    ];
     return [
       `${scope}/${packageName}`,
       `${scope}/docusaurus-${moduleType}-${packageName}`,
diff --git a/packages/docusaurus/src/server/plugins/routeConfig.ts b/packages/docusaurus/src/server/plugins/routeConfig.ts
index e9b7c589408f..3731eb993d74 100644
--- a/packages/docusaurus/src/server/plugins/routeConfig.ts
+++ b/packages/docusaurus/src/server/plugins/routeConfig.ts
@@ -50,8 +50,8 @@ export function sortConfig(
     }
     // Higher priority get placed first.
     if (a.priority || b.priority) {
-      const priorityA = a.priority || 0;
-      const priorityB = b.priority || 0;
+      const priorityA = a.priority ?? 0;
+      const priorityB = b.priority ?? 0;
       const score = priorityB - priorityA;
 
       if (score !== 0) {
diff --git a/packages/docusaurus/src/server/plugins/synthetic.ts b/packages/docusaurus/src/server/plugins/synthetic.ts
index 67e297ffe5f5..5d4fe38b4d01 100644
--- a/packages/docusaurus/src/server/plugins/synthetic.ts
+++ b/packages/docusaurus/src/server/plugins/synthetic.ts
@@ -89,7 +89,7 @@ export function createMDXFallbackPlugin({
       // processed by content plugins mdx loaders. This works, but a bit
       // hacky... Not sure there's a way to handle that differently in webpack
       function getMDXFallbackExcludedPaths(): string[] {
-        const rules: RuleSetRule[] = config?.module?.rules as RuleSetRule[];
+        const rules: RuleSetRule[] = config.module?.rules as RuleSetRule[];
         return rules.flatMap((rule) => {
           const isMDXRule =
             rule.test instanceof RegExp && rule.test.test('x.mdx');
diff --git a/packages/docusaurus/src/server/routes.ts b/packages/docusaurus/src/server/routes.ts
index ab97b1a7b9d7..b13c8cd9b11a 100644
--- a/packages/docusaurus/src/server/routes.ts
+++ b/packages/docusaurus/src/server/routes.ts
@@ -152,7 +152,7 @@ const isModule = (value: unknown): value is Module =>
   typeof value === 'string' ||
   (typeof value === 'object' &&
     // eslint-disable-next-line no-underscore-dangle
-    !!(value as {[key: string]: unknown})?.__import);
+    !!(value as {[key: string]: unknown} | null)?.__import);
 
 /**
  * Takes a {@link Module} (which is nothing more than a path plus some metadata
diff --git a/packages/docusaurus/src/server/translations/translationsExtractor.ts b/packages/docusaurus/src/server/translations/translationsExtractor.ts
index 6113b23ba933..83be6bcd7503 100644
--- a/packages/docusaurus/src/server/translations/translationsExtractor.ts
+++ b/packages/docusaurus/src/server/translations/translationsExtractor.ts
@@ -160,7 +160,7 @@ export async function extractSourceCodeFileTranslations(
       filename: sourceCodeFilePath,
     }) as Node;
 
-    const translations = await extractSourceCodeAstTranslations(
+    const translations = extractSourceCodeAstTranslations(
       ast,
       sourceCodeFilePath,
     );
@@ -243,9 +243,7 @@ Full code: ${generate(node).code}`;
             .find(
               (attr) =>
                 attr.isJSXAttribute() &&
-                (attr as NodePath<t.JSXAttribute>)
-                  .get('name')
-                  .isJSXIdentifier({name: propName}),
+                attr.get('name').isJSXIdentifier({name: propName}),
             );
 
           if (attributePath) {
diff --git a/packages/docusaurus/src/webpack/base.ts b/packages/docusaurus/src/webpack/base.ts
index 4e00fecefaf1..0b66a8d539be 100644
--- a/packages/docusaurus/src/webpack/base.ts
+++ b/packages/docusaurus/src/webpack/base.ts
@@ -38,7 +38,7 @@ export function excludeJS(modulePath: string): boolean {
   }
   // Don't transpile node_modules except any docusaurus npm package
   return (
-    /node_modules/.test(modulePath) &&
+    modulePath.includes('node_modules') &&
     !/docusaurus(?:(?!node_modules).)*\.jsx?$/.test(modulePath) &&
     !LibrariesToTranspileRegex.test(modulePath)
   );
diff --git a/packages/docusaurus/src/webpack/plugins/CleanWebpackPlugin.ts b/packages/docusaurus/src/webpack/plugins/CleanWebpackPlugin.ts
index 5a8f4770102a..a87d2dcfda05 100644
--- a/packages/docusaurus/src/webpack/plugins/CleanWebpackPlugin.ts
+++ b/packages/docusaurus/src/webpack/plugins/CleanWebpackPlugin.ts
@@ -116,7 +116,7 @@ export default class CleanWebpackPlugin {
   }
 
   apply(compiler: Compiler): void {
-    if (!compiler.options.output || !compiler.options.output.path) {
+    if (!compiler.options.output.path) {
       console.warn(
         'clean-webpack-plugin: options.output.path not defined. Plugin disabled...',
       );
@@ -185,7 +185,7 @@ export default class CleanWebpackPlugin {
      * (relies on del's cwd: outputPath option)
      */
     const staleFiles = this.currentAssets.filter(
-      (previousAsset) => assets.includes(previousAsset) === false,
+      (previousAsset) => !assets.includes(previousAsset),
     );
 
     /**
@@ -198,7 +198,7 @@ export default class CleanWebpackPlugin {
     /**
      * Remove unused webpack assets
      */
-    if (this.cleanStaleWebpackAssets === true && staleFiles.length !== 0) {
+    if (this.cleanStaleWebpackAssets && staleFiles.length !== 0) {
       removePatterns.push(...staleFiles);
     }
 
@@ -234,10 +234,9 @@ export default class CleanWebpackPlugin {
         });
       }
     } catch (err) {
-      const needsForce =
-        /Cannot delete files\/folders outside the current working directory\./.test(
-          (err as Error).message,
-        );
+      const needsForce = (err as Error).message.includes(
+        'Cannot delete files/folders outside the current working directory.',
+      );
 
       if (needsForce) {
         const message =
diff --git a/packages/docusaurus/src/webpack/utils.ts b/packages/docusaurus/src/webpack/utils.ts
index 79362887679e..8a7d0aef6120 100644
--- a/packages/docusaurus/src/webpack/utils.ts
+++ b/packages/docusaurus/src/webpack/utils.ts
@@ -185,13 +185,11 @@ export function applyConfigureWebpack(
   if (typeof configureWebpack === 'function') {
     const {mergeStrategy, ...res} =
       configureWebpack(config, isServer, utils, content) ?? {};
-    if (res && typeof res === 'object') {
-      const customizeRules = mergeStrategy ?? {};
-      return mergeWithCustomize({
-        customizeArray: customizeArray(customizeRules),
-        customizeObject: customizeObject(customizeRules),
-      })(config, res);
-    }
+    const customizeRules = mergeStrategy ?? {};
+    return mergeWithCustomize({
+      customizeArray: customizeArray(customizeRules),
+      customizeObject: customizeObject(customizeRules),
+    })(config, res);
   }
   return config;
 }
@@ -243,7 +241,7 @@ export function compile(config: Configuration[]): Promise<void> {
     const compiler = webpack(config);
     compiler.run((err, stats) => {
       if (err) {
-        logger.error(err.stack || err);
+        logger.error(err.stack ?? err);
         if (err.details) {
           logger.error(err.details);
         }
diff --git a/packages/lqip-loader/src/index.ts b/packages/lqip-loader/src/index.ts
index 6bb0eb526240..5dd78269439c 100644
--- a/packages/lqip-loader/src/index.ts
+++ b/packages/lqip-loader/src/index.ts
@@ -17,9 +17,7 @@ export default async function lqipLoader(
   this: LoaderContext<Options>,
   contentBuffer: Buffer,
 ): Promise<void> {
-  if (this.cacheable) {
-    this.cacheable();
-  }
+  this.cacheable();
   const callback = this.async();
   const imgPath = this.resourcePath;
   let content = contentBuffer.toString('utf8');
diff --git a/packages/stylelint-copyright/src/index.ts b/packages/stylelint-copyright/src/index.ts
index a620d184d0a0..0b591561ea0e 100644
--- a/packages/stylelint-copyright/src/index.ts
+++ b/packages/stylelint-copyright/src/index.ts
@@ -27,7 +27,8 @@ const plugin = stylelint.createPlugin(
         },
         {
           actual: secondaryOption,
-          possible: (v) => typeof (v as SecondaryOption)?.header === 'string',
+          possible: (v) =>
+            typeof (v as SecondaryOption | undefined)?.header === 'string',
         },
       );
 
@@ -42,7 +43,7 @@ const plugin = stylelint.createPlugin(
         }
       }
       if (context.fix) {
-        root.first?.before(`/*${secondaryOption.header}\n */`);
+        root.first?.before(`/*${secondaryOption.header!}\n */`);
         return;
       }
 
diff --git a/website/_dogfooding/docs-tests-sidebars.js b/website/_dogfooding/docs-tests-sidebars.js
index 6b8b8f9c4365..e7ebb55ce1a5 100644
--- a/website/_dogfooding/docs-tests-sidebars.js
+++ b/website/_dogfooding/docs-tests-sidebars.js
@@ -5,7 +5,12 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-/** @type {import('@docusaurus/plugin-content-docs').SidebarsConfig} */
+/**
+ * @typedef {import('@docusaurus/plugin-content-docs').SidebarsConfig} SidebarsConfig
+ * @typedef {import('@docusaurus/plugin-content-docs/lib/sidebars/types').SidebarItemConfig} SidebarItemConfig
+ */
+
+/** @type {SidebarsConfig} */
 const sidebars = {
   sidebar: [
     {
@@ -119,6 +124,11 @@ function generateHugeSidebarItems() {
   const linksCount = 8;
   const categoriesCount = 8;
 
+  /**
+   * @param {number} maxLevel
+   * @param {number} currentLevel
+   * @returns {SidebarItemConfig[]}
+   */
   function generateRecursive(maxLevel, currentLevel = 0) {
     if (currentLevel === maxLevel) {
       return [
@@ -130,17 +140,19 @@ function generateHugeSidebarItems() {
       ];
     }
 
-    const linkItems = [...Array(linksCount).keys()].map((index) => ({
+    const linkItems = Array.from(Array(linksCount).keys()).map((index) => ({
       type: 'link',
       href: '/',
       label: `Link ${index} (level ${currentLevel + 1})`,
     }));
 
-    const categoryItems = [...Array(categoriesCount).keys()].map((index) => ({
-      type: 'category',
-      label: `Category ${index} (level ${currentLevel + 1})`,
-      items: generateRecursive(maxLevel, currentLevel + 1),
-    }));
+    const categoryItems = Array.from(Array(categoriesCount).keys()).map(
+      (index) => ({
+        type: 'category',
+        label: `Category ${index} (level ${currentLevel + 1})`,
+        items: generateRecursive(maxLevel, currentLevel + 1),
+      }),
+    );
 
     return [...linkItems, ...categoryItems];
   }
diff --git a/website/_dogfooding/testSwizzleThemeClassic.mjs b/website/_dogfooding/testSwizzleThemeClassic.mjs
index ab75a7d1dafb..6f635bea5718 100644
--- a/website/_dogfooding/testSwizzleThemeClassic.mjs
+++ b/website/_dogfooding/testSwizzleThemeClassic.mjs
@@ -10,15 +10,16 @@ import fs from 'fs-extra';
 import {fileURLToPath} from 'url';
 import logger from '@docusaurus/logger';
 
-import ClassicTheme from '@docusaurus/theme-classic';
+import classicTheme from '@docusaurus/theme-classic';
 
 // Unsafe imports
 import {readComponentNames} from '@docusaurus/core/lib/commands/swizzle/components.js';
 import {normalizeSwizzleConfig} from '@docusaurus/core/lib/commands/swizzle/config.js';
 import {wrap, eject} from '@docusaurus/core/lib/commands/swizzle/actions.js';
 
-const swizzleConfig = normalizeSwizzleConfig(ClassicTheme.getSwizzleConfig());
+const swizzleConfig = normalizeSwizzleConfig(classicTheme.getSwizzleConfig());
 
+/** @type {"eject" | "wrap"} */
 const action = process.env.SWIZZLE_ACTION ?? 'eject';
 const typescript = process.env.SWIZZLE_TYPESCRIPT === 'true';
 
@@ -81,14 +82,12 @@ if (action === 'wrap') {
   });
 }
 
+/**
+ * @param {string} componentName
+ */
 function getActionStatus(componentName) {
   const actionStatus =
     swizzleConfig.components[componentName]?.actions[action] ?? 'unsafe';
-  if (!actionStatus) {
-    throw new Error(
-      `Unexpected: missing action ${action} for ${componentName}`,
-    );
-  }
   return actionStatus;
 }
 
diff --git a/website/delayCrowdin.mjs b/website/delayCrowdin.mjs
index d212e0e7c9a0..2fbb232c2f47 100644
--- a/website/delayCrowdin.mjs
+++ b/website/delayCrowdin.mjs
@@ -13,6 +13,9 @@ And then both try to dl the translations at the same time, and then we have a
 Used in conjunction with waitForCrowdin.js (which is not enough)
  */
 
+/**
+ * @param {number} ms
+ */
 async function delay(ms) {
   return new Promise((resolve) => {
     setTimeout(resolve, ms);
diff --git a/website/docusaurus.config.js b/website/docusaurus.config.js
index 4fe18ec4dfb3..6885a87f8667 100644
--- a/website/docusaurus.config.js
+++ b/website/docusaurus.config.js
@@ -49,7 +49,7 @@ const isDeployPreview =
 // Used to debug production build issues faster
 const isBuildFast = !!process.env.BUILD_FAST;
 
-const baseUrl = process.env.BASE_URL || '/';
+const baseUrl = process.env.BASE_URL ?? '/';
 
 // Special deployment for staging locales until they get enough translations
 // https://app.netlify.com/sites/docusaurus-i18n-staging
diff --git a/website/src/components/APITable/index.tsx b/website/src/components/APITable/index.tsx
index fb2e69366fde..b6a73d2862cf 100644
--- a/website/src/components/APITable/index.tsx
+++ b/website/src/components/APITable/index.tsx
@@ -68,8 +68,8 @@ const APITableRowComp = React.forwardRef(APITableRow);
  */
 export default function APITable({children, name}: Props): JSX.Element {
   const [thead, tbody] = React.Children.toArray(children.props.children) as [
-    ReactElement,
-    ReactElement,
+    ReactElement<{children: ReactElement[]}>,
+    ReactElement<{children: ReactElement[]}>,
   ];
   const highlightedRow = useRef<HTMLTableRowElement>(null);
   useEffect(() => {
diff --git a/website/src/components/ColorGenerator/index.tsx b/website/src/components/ColorGenerator/index.tsx
index 87e68c528682..7fbcdfa03b60 100644
--- a/website/src/components/ColorGenerator/index.tsx
+++ b/website/src/components/ColorGenerator/index.tsx
@@ -59,7 +59,9 @@ export default function ColorGenerator(): JSX.Element {
 
   // Switch modes -> update state by stored values
   useEffect(() => {
-    const storedValues: ColorState = JSON.parse(storage.get() ?? '{}');
+    const storedValues = JSON.parse(
+      storage.get() ?? '{}',
+    ) as Partial<ColorState>;
     setInputColor(storedValues.baseColor ?? DEFAULT_PRIMARY_COLOR);
     setBaseColor(storedValues.baseColor ?? DEFAULT_PRIMARY_COLOR);
     setBackground(storedValues.background ?? DEFAULT_BACKGROUND_COLOR);
diff --git a/website/src/components/TeamProfileCards/index.tsx b/website/src/components/TeamProfileCards/index.tsx
index 92b6858df745..d1b3d506291b 100644
--- a/website/src/components/TeamProfileCards/index.tsx
+++ b/website/src/components/TeamProfileCards/index.tsx
@@ -12,7 +12,7 @@ import Link from '@docusaurus/Link';
 function WebsiteLink({to, children}: {to: string; children?: ReactNode}) {
   return (
     <Link to={to}>
-      {children || (
+      {children ?? (
         <Translate id="team.profile.websiteLinkLabel">website</Translate>
       )}
     </Link>
@@ -23,7 +23,7 @@ type ProfileProps = {
   className?: string;
   name: string;
   children: ReactNode;
-  githubUrl?: string;
+  githubUrl: string;
   twitterUrl?: string;
 };
 
diff --git a/website/src/pages/index.tsx b/website/src/pages/index.tsx
index 6937b6da4ed2..00903c3c7b60 100644
--- a/website/src/pages/index.tsx
+++ b/website/src/pages/index.tsx
@@ -99,7 +99,7 @@ function MigrationAnnouncement() {
 }
 
 function TweetsSection() {
-  const tweetColumns: Array<Array<TweetItem>> = [[], [], []];
+  const tweetColumns: TweetItem[][] = [[], [], []];
   Tweets.filter((tweet) => tweet.showOnHomepage).forEach((tweet, i) =>
     tweetColumns[i % 3]!.push(tweet),
   );
diff --git a/website/src/pages/showcase/_components/ShowcaseFilterToggle/index.tsx b/website/src/pages/showcase/_components/ShowcaseFilterToggle/index.tsx
index acb4516d111f..aaada5d7618f 100644
--- a/website/src/pages/showcase/_components/ShowcaseFilterToggle/index.tsx
+++ b/website/src/pages/showcase/_components/ShowcaseFilterToggle/index.tsx
@@ -35,7 +35,7 @@ export default function ShowcaseFilterToggle(): JSX.Element {
     const searchParams = new URLSearchParams(location.search);
     searchParams.delete(OperatorQueryKey);
     if (!operator) {
-      searchParams.append(OperatorQueryKey, operator ? 'OR' : 'AND');
+      searchParams.append(OperatorQueryKey, 'AND');
     }
     history.push({
       ...location,
diff --git a/website/src/pages/showcase/_components/ShowcaseTooltip/index.tsx b/website/src/pages/showcase/_components/ShowcaseTooltip/index.tsx
index bcbf5b4709b8..7087fa0e5d2d 100644
--- a/website/src/pages/showcase/_components/ShowcaseTooltip/index.tsx
+++ b/website/src/pages/showcase/_components/ShowcaseTooltip/index.tsx
@@ -14,7 +14,6 @@ interface Props {
   anchorEl?: HTMLElement | string;
   id: string;
   text: string;
-  delay?: number;
   children: React.ReactElement;
 }
 
@@ -23,7 +22,6 @@ export default function Tooltip({
   id,
   anchorEl,
   text,
-  delay,
 }: Props): JSX.Element {
   const [open, setOpen] = useState(false);
   const [referenceElement, setReferenceElement] = useState<HTMLElement | null>(
@@ -84,7 +82,7 @@ export default function Tooltip({
 
       timeout.current = window.setTimeout(() => {
         setOpen(true);
-      }, delay || 400);
+      }, 400);
     };
 
     const handleClose = () => {
@@ -113,7 +111,7 @@ export default function Tooltip({
         });
       }
     };
-  }, [referenceElement, text, delay]);
+  }, [referenceElement, text]);
 
   return (
     <>
diff --git a/website/src/pages/versions.tsx b/website/src/pages/versions.tsx
index 9db0ec5d10ee..4a65419b8837 100644
--- a/website/src/pages/versions.tsx
+++ b/website/src/pages/versions.tsx
@@ -58,38 +58,35 @@ export default function Version(): JSX.Element {
           </Translate>
         </Heading>
 
-        {latestVersion && (
-          <div className="margin-bottom--lg">
-            <Heading as="h3" id="next">
-              <Translate id="versionsPage.current.title">
-                Current version (Stable)
-              </Translate>
-            </Heading>
-            <p>
-              <Translate id="versionsPage.current.description">
-                Here you can find the documentation for current released
-                version.
-              </Translate>
-            </p>
-            <table>
-              <tbody>
-                <tr>
-                  <th>{latestVersion.label}</th>
-                  <td>
-                    <Link to={latestVersion.path}>
-                      <DocumentationLabel />
-                    </Link>
-                  </td>
-                  <td>
-                    <a href={`${repoUrl}/releases/tag/v${latestVersion.name}`}>
-                      <ReleaseNotesLabel />
-                    </a>
-                  </td>
-                </tr>
-              </tbody>
-            </table>
-          </div>
-        )}
+        <div className="margin-bottom--lg">
+          <Heading as="h3" id="next">
+            <Translate id="versionsPage.current.title">
+              Current version (Stable)
+            </Translate>
+          </Heading>
+          <p>
+            <Translate id="versionsPage.current.description">
+              Here you can find the documentation for current released version.
+            </Translate>
+          </p>
+          <table>
+            <tbody>
+              <tr>
+                <th>{latestVersion.label}</th>
+                <td>
+                  <Link to={latestVersion.path}>
+                    <DocumentationLabel />
+                  </Link>
+                </td>
+                <td>
+                  <a href={`${repoUrl}/releases/tag/v${latestVersion.name}`}>
+                    <ReleaseNotesLabel />
+                  </a>
+                </td>
+              </tr>
+            </tbody>
+          </table>
+        </div>
 
         {currentVersion !== latestVersion && (
           <div className="margin-bottom--lg">
diff --git a/website/src/theme/ColorModeToggle.tsx b/website/src/theme/ColorModeToggle.tsx
index 44f81a00ff66..85e886bc75b8 100644
--- a/website/src/theme/ColorModeToggle.tsx
+++ b/website/src/theme/ColorModeToggle.tsx
@@ -32,7 +32,9 @@ export default function ColorModeToggle(props: Props): JSX.Element {
         props.onChange(colorMode);
         const isDarkMode = colorMode === 'dark';
         const storage = isDarkMode ? darkStorage : lightStorage;
-        const colorState: ColorState = JSON.parse(storage.get() ?? 'null') ?? {
+        const colorState = (JSON.parse(
+          storage.get() ?? 'null',
+        ) as ColorState | null) ?? {
           baseColor: isDarkMode ? DARK_PRIMARY_COLOR : LIGHT_PRIMARY_COLOR,
           background: isDarkMode
             ? DARK_BACKGROUND_COLOR
diff --git a/website/testCSSOrder.mjs b/website/testCSSOrder.mjs
index 9594c9ab3286..62422e3d4ea8 100644
--- a/website/testCSSOrder.mjs
+++ b/website/testCSSOrder.mjs
@@ -84,9 +84,14 @@ if (missingCSSMarkers.length > 0) {
 }
 
 // https://github.com/you-dont-need/You-Dont-Need-Lodash-Underscore#_sortby-and-_orderby
-const sortBy = (key) => (a, b) =>
-  // eslint-disable-next-line no-nested-ternary
-  a[key] > b[key] ? 1 : b[key] > a[key] ? -1 : 0;
+const sortBy =
+  (/** @type {string} */ key) =>
+  (
+    /** @type {Record<string, unknown>} */ a,
+    /** @type {Record<string, unknown>} */ b,
+  ) =>
+    // eslint-disable-next-line no-nested-ternary
+    a[key] > b[key] ? 1 : b[key] > a[key] ? -1 : 0;
 
 const sortedCSSMarkers = [...cssMarkersWithPositions]
   .sort(sortBy('position'))
diff --git a/website/waitForCrowdin.mjs b/website/waitForCrowdin.mjs
index d8e2823b5008..7a02bf0a4ed6 100644
--- a/website/waitForCrowdin.mjs
+++ b/website/waitForCrowdin.mjs
@@ -28,6 +28,9 @@ const token = process.env.CROWDIN_PERSONAL_TOKEN; // Set on Netlify
 
 const translations = new Translations({token});
 
+/**
+ * @param {number} ms
+ */
 async function delay(ms) {
   return new Promise((resolve) => {
     setTimeout(resolve, ms);