diff --git a/packages/happy-dom/src/custom-element/CustomElementRegistry.ts b/packages/happy-dom/src/custom-element/CustomElementRegistry.ts
index 53382a7c0..496e93c51 100644
--- a/packages/happy-dom/src/custom-element/CustomElementRegistry.ts
+++ b/packages/happy-dom/src/custom-element/CustomElementRegistry.ts
@@ -9,6 +9,37 @@ export default class CustomElementRegistry {
 	public _registry: { [k: string]: { elementClass: typeof HTMLElement; extends: string } } = {};
 	public _callbacks: { [k: string]: (() => void)[] } = {};
 
+	/**
+	 * Validates the correctness of custom element tag names.
+	 *
+	 * @param tagName custom element tag name.
+	 * @returns boolean True, if tag name is standard compliant.
+	 */
+	private isValidCustomElementName(tagName: string): boolean {
+		// Validation criteria based on:
+		// https://html.spec.whatwg.org/multipage/custom-elements.html#valid-custom-element-name
+		const PCENChar =
+			'[-_.]|[0-9]|[a-z]|\u{B7}|[\u{C0}-\u{D6}]|[\u{D8}-\u{F6}]' +
+			'|[\u{F8}-\u{37D}]|[\u{37F}-\u{1FFF}]' +
+			'|[\u{200C}-\u{200D}]|[\u{203F}-\u{2040}]|[\u{2070}-\u{218F}]' +
+			'|[\u{2C00}-\u{2FEF}]|[\u{3001}-\u{D7FF}]' +
+			'|[\u{F900}-\u{FDCF}]|[\u{FDF0}-\u{FFFD}]|[\u{10000}-\u{EFFFF}]';
+
+		const PCEN = new RegExp(`^[a-z](${PCENChar})*-(${PCENChar})*$`, 'u');
+
+		const forbiddenNames = [
+			'annotation-xml',
+			'color-profile',
+			'font-face',
+			'font-face-src',
+			'font-face-uri',
+			'font-face-format',
+			'font-face-name',
+			'missing-glyph'
+		];
+		return PCEN.test(tagName) && !forbiddenNames.includes(tagName);
+	}
+
 	/**
 	 * Defines a custom element class.
 	 *
diff --git a/packages/happy-dom/test/custom-element/CustomElementRegistry.test.ts b/packages/happy-dom/test/custom-element/CustomElementRegistry.test.ts
index 51637a923..50e96fda0 100644
--- a/packages/happy-dom/test/custom-element/CustomElementRegistry.test.ts
+++ b/packages/happy-dom/test/custom-element/CustomElementRegistry.test.ts
@@ -10,6 +10,20 @@ describe('CustomElementRegistry', () => {
 		CustomElement.observedAttributesCallCount = 0;
 	});
 
+	describe('isValidCustomElementName()', () => {
+		it('Validate custom elements tag name.', () => {
+			expect(customElements.isValidCustomElementName('a-b')).toBe(true);
+			expect(customElements.isValidCustomElementName('2a-b')).toBe(false);
+			expect(customElements.isValidCustomElementName('a2-b')).toBe(true);
+			expect(customElements.isValidCustomElementName('A-B')).toBe(false);
+			expect(customElements.isValidCustomElementName('aB-c')).toBe(false);
+			expect(customElements.isValidCustomElementName('ab')).toBe(false);
+			expect(customElements.isValidCustomElementName('a-\u00d9')).toBe(true);
+			expect(customElements.isValidCustomElementName('a_b.c-d')).toBe(true);
+			expect(customElements.isValidCustomElementName('font-face')).toBe(false);
+		});
+	});
+
 	describe('define()', () => {
 		it('Defines an HTML element and returns it with get().', () => {
 			customElements.define('custom-element', CustomElement);
@@ -43,7 +57,7 @@ describe('CustomElementRegistry', () => {
 	});
 
 	describe('get()', () => {
-		it('Returns element class if the tag name has been defined..', () => {
+		it('Returns element class if the tag name has been defined.', () => {
 			customElements.define('custom-element', CustomElement);
 			expect(customElements.get('custom-element')).toBe(CustomElement);
 		});