My Oneplus 6T developed a problem after getting an update. If I'm not using YouTube then all videos are cropped in to take up the whole screen, chopping off content. This happened for whatever browser I was using, including Chrome. Getting Firefox and this add-on solved that. I guess the only thing I could ask for is being able to pinch or unpinch to change the modes (normal/upscale/stretch) or something like that. That way I don't have to open the menu to change it if I ever want to.

Edit: for those of you unable to use this, check out F-Droid and Fennec. F-Droid is an open source Android repository (think of it as a 3rd party app store for free/open source apps. Fennec is a free and open-source version of Firefox, and using Fennec you can download the specific older version of Firefox(Fennec) that allowed non recommended add-ons like this. I believe it was version 68.12.0

I use it in firefox nightly for android, so I can see youtube without cropping . 5 stars for the extension! Not so much for firefox.

thank you, needed this for crunchyroll

Really nice extension.. Works like a magic for new Firefox android

Works and has a gorgeous simple interface.

Funcionó fantástico en Firefox for Android Nightly. Ya no tengo problema al visualizar cualquier video.

UtraWimeo is the only one that actually works, I tried many other addons and wasted a lot of time for this. If this didn't work, I would need to be spending money for bigger monitor on computer I rarely use. Email answer was great also. This plugin is also private, nothing is sent out of computer.

Thanks, this fixed youtube cropped videos in fullscreen landscape mode

I'm using this with a 4:3 CRT and it's amazing. Works on HBO, Youtube, everything I've tried so far. Great for old 4:3 movies and videos that were uploaded with forced 16:9 pillarboxing, to put them back in fullscreen like they should be.

Работает нормально. При случае, когда очень хочется, всегда можно пожертвовать кусочком экрана 16:9 сверху-снизу, чтобы растянуть изображение на полный 21:9 экран

I'm using it on my Samsung Galaxy A51 (Android 10) after the top and the bottom from YouTube-Videos was cutted and it works perfect! Now I can watch YouTube-Videos completely, from top to bottom! Very good work!I really hope, this Add-On will be supported at the new Firefox for Android and Firefox Nightly!

Works for Amazon Prime Video. Thanks!

Thanks to the creators! Wanted this for Amazon Prime Video, and it worked!