If this add-ons build from the same source-code on author github (https://github.com/lennonhill/cookies-txt), than it's safe to use, no privacy or malicious codes found. I using it with youtube-dl and it's work fine.

Somebody complained that they installed this extension but then found no way to use it. I had the same problem - at first. The icon that's supposed to appear in the toolbar didn't. But it turned out I had the same problem with other extensions. Firefox was somehow stuck in a state where no extensions worked. I found the problem described in several places. I tried 2 or 3 suggested solutions but none of them worked. In the end I uninstalled and reinstalled firefox. That did it. Cookies.txt now does the job.

Does its job

first save container cookies later save main cookies

Использовал для youtube-dl. Всё сработало.

great

Works well but lacks the ability to export cookies for a certain domain.

This tool is great, but I'd like to have an option to filter by domain.

Just works! One video was unable to download via 'youtube-dl', but after I exported cookies.txt with this extension, my download was successfull!

youtube-dl --cookies cookies.txt "https://www.youtube.com/watch?v=......."