Download YouTube videos. Video formats are listed at the top of the watch page. Video links are tagged so that they can be downloaded easily.
Do you have a link to the video?
For example: https://www.youtube.com/watch?v=dI0cfw0LJFo
Can you check if it works now? It works for me in Firefox 83.
The 720p video is not working, probably because YouTube has removed the video but not updated the metadata. The other links are okay. (So is 720p on other videos.)
The script doesn't work in Edge 44, there seems to be some script error somewhere.
v2.41 should work in Edge, give it a try.
Somehow, the RegExp works a little differently in Edge and is too aggressive, causing some sort of "denial-of-service" as it tries to scan the HTML file for the best match.
This could be what's happening in other browsers too. Maybe it isn't fixed by YouTube, but the browsers. (May be due to the RegExp library used.)
I've also enabled copy-to-clipboard for Edge since I found that Edge no longer prompts to download when you click on the links. It will play the video instead.
This script worked recently. But when I try video from using this script on 2 browsers (Microsoft Edge and Mozilla Firefox), browsers always says “Couldn't Download: Network Issue” (Microsoft Edge) and “{File Location URL} could not be saved. Because the source file could not be read. Try again later or contact the server administrator.” (Mozilla Firefox).