Anything wrong with the Screen Capture built in to Firefox in the Address Bar on the 3 Dot Menu ? https://addons.mozilla.org/en-US/firefox/extensions/

Please let us know if this solved your issue or if need further assistance.

I'm talking about video, not screenshot. Thanks

AssafMalki said

I'm talking about video, not screenshot. Thanks

Please put Video Recorder in the search box in the URL from question. Support does not recommend.

What do you mean? Should I change the subject of the question to mention video? Thanks

Look for your own Video Recorder Software Extension or stand alone. Think you can Open the URL https://addons.mozilla.org/en-US/firefox/extensions/ and put that in the search box and review what is there that suits your purposes.

There is only one video recorder add-on :

https://addons.mozilla.org/en-US/firefox/addon/video-recorder-webextension/

(has nothing to do with 'screen recording' .... )