diff --git a/README.md b/README.md
index 5a93f825c4e8e..b97ac63d9e384 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,8 @@ Feel free to stop by our [Matrix room](https://chat.mozilla.org/#/room/#pdfjs:mo
 ### Online demo
 
 Please note that the "Modern browsers" version assumes native support for
-features such as e.g. `async`/`await`, and `ReadableStream`.
+features such as e.g. `async`/`await`, `ReadableStream`, optional chaining, and
+nullish coalescing.
 
 + Modern browsers: https://mozilla.github.io/pdf.js/web/viewer.html
 
@@ -70,7 +71,7 @@ and then you can open:
 
 + http://localhost:8888/web/viewer.html
 
-Please keep in mind that this requires an ES6 compatible browser; refer to [Building PDF.js](https://github.com/mozilla/pdf.js/blob/master/README.md#building-pdfjs) for usage with older browsers.
+Please keep in mind that this requires a modern and fully up-to-date browser; refer to [Building PDF.js](https://github.com/mozilla/pdf.js/blob/master/README.md#building-pdfjs) for non-development usage of the PDF.js library.
 
 It is also possible to view all test PDF files on the right side by opening:
 
@@ -83,7 +84,11 @@ viewer, run:
 
     $ gulp generic
 
-This will generate `pdf.js` and `pdf.worker.js` in the `build/generic/build/` directory.
+If you need to support older browsers, run:
+
+    $ gulp generic-es5
+
+This will generate `pdf.js` and `pdf.worker.js` in the `build/generic/build/` directory (respectively `build/generic-es5/build/`).
 Both scripts are needed but only `pdf.js` needs to be included since `pdf.worker.js` will
 be loaded by `pdf.js`. The PDF.js files are large and should be minified for production.
 
diff --git a/docs/contents/getting_started/index.md b/docs/contents/getting_started/index.md
index b3328734adbe3..63fcbabe93c90 100644
--- a/docs/contents/getting_started/index.md
+++ b/docs/contents/getting_started/index.md
@@ -49,7 +49,7 @@ Before downloading PDF.js please take a moment to understand the different layer
     </span>
   </div>
   <div class="col-md-4">
-    <h3>Prebuilt (ES5-compatible)</h3>
+    <h3>Prebuilt (for older browsers)</h3>
     <p>
       Includes the generic build of PDF.js and the viewer.
     </p>
diff --git a/external/dist/README.md b/external/dist/README.md
index 6baa2e5809961..75109c2bbb6d9 100644
--- a/external/dist/README.md
+++ b/external/dist/README.md
@@ -7,7 +7,8 @@ parsing and rendering PDFs.
 This is a pre-built version of the PDF.js source code. It is automatically
 generated by the build scripts.
 
-For usage with older browsers/environments, without support for modern features
-such as e.g. `async`/`await`, and `ReadableStream`, please see the `es5` folder.
+For usage with older browsers or environments, without support for modern
+features such as e.g. `async`/`await`, `ReadableStream`, optional chaining, and
+nullish coalescing; please see the `es5` folder.
 
 See https://github.com/mozilla/pdf.js for learning and contributing.