Is there a way to override aspect ratio in Youtube?

Hello!

I tried YouTube in many browsers and I could not find a way to override the aspect ratio of a video. I watch some old videos that are 4:3 and appear with undesirable black bars at the side of the screen in either window or full screen mode.

It seems the only workaround is to copy the YouTube URL of the video you want to watch and then open it with VLC. Media Player Classic Black Edition, or other compatible media player. Once opened in the media player you can adjust several quality features, including forcing the aspect ratio to 16:9 to fill the screen.

Is there any addon for Firefox or Chrome that can override the aspect ratio of YouTube videos (or other online videos in general) through the browser without having to copy-paste the URL to a compatible player? Or alternatively, could I configure a media player to open automatically when watching YouTube videos?

I would also like to share a tip:

I noticed that latest version of VLC (3.0.8) cannot open YouTube URLs any more (it had no problem a few weeks ago). I Googled the issue and discovered that VLC is using a library file called youtube.lua to open YouTube videos and this has been updated, but VLC is not yet updated. So the old version of youtube.lua that comes with VLC doesn't open the URLs.

You can find the latest version in GitHub. Click on the link to open the site, then right-click on the Raw button and select Save link as to download the file. You must then rename it from youtube.lua to youtube.luac and copy-paste it in the folder c:\Program Files\VideoLAN\VLC\lua\playlist replacing the old file. Now VLC can play YouTube URLs again.

Hello!

I downloaded and installed the addon, but could not figure out how to stretch the image to fill the screen. Could you guide me please? Thank you in advance.

Nothing about changing the aspect ratio in the guide. I posted a question at the site.