Using Firefox ESR version 68? or some other old version? Use version 1.6 of this add-on: https://addons.mozilla.org/en-US/firefox/addon/live-recorder/versions/ and disable auto-updates from the about:addons. Record audio, video, and canvas elements into webm, in real time. To try it out:

Go to a website with video or audio, like youtube, for example.
Hit the addon button and you should see bar (see screenshots).
- Some websites, like Soundcloud, serve media differently, it won't work on those and the status bar will not appear then.
Click the button and it'll start recording. You might see the video start stuttering, but the recording should be fine.
Once you hit stop, the recording will be offered to you.
Wa la.

A Firefox bug causes the duration metadata to go missing. Fix it with: ffmpeg -i YOUR_FILE.webm -c:v copy -c:a copy output.webm If you want to change audio and video codecs, then your go-to option is to use an external program. Here is an example, changing audio codec to vorbis with ffmpeg: ffmpeg -i input.webm -acodec libvorbis -vcodec copy out.webm The recording's audio codec depends on the source, often opus. Video is always(?) vp8 webm. For now, the recording FPS is 60, because there's no way of changing it. Hopefully this can be fixed sometime. Here's an ffmpeg command to turn it into 30fps+vorbis. ffmpeg -i in.webm -acodec libvorbis -vcodec vp8 -r 30 out.webm https://gitlab.com/losnappas/live-recorder/ If you like it then consider donating some money to charity. https://www.crowdrise.com/horn-of-africa/fundraiser/lynn99