If you’re unable to watch YouTube.com videos on fullscreen mode while using Firefox Lite, that’s because there is a known issue with Android WebView which handles the way apps like Firefox Lite load web pages.
On Android 7 and later
Google Chrome 51+ and WebView are packaged together in this version. Updating Chrome will also update WebView.
- Visit the Chrome page on the Google Play store.
- Tap the button to download or install the update.
On Android 6 and earlier
This has been fixed in an upcoming version of WebView (74.0.3729.108) which will be released in the Google Play store. When the new version of WebView is released, update your system software and Firefox Lite to get the new fix:
- Visit the Android System Webview Google Play page.
- Tap the button to download or install the update (please make sure it’s version 74.0.3729.108). You can see the version number by scrolling down the Google Play page to Additional information.