If we use this official example: https://webrtc.github.io/samples/src/content/getusermedia/record/ we'll be able to record and download videos. This videos can be played in our computer, but have issues if we want to upload them to other platforms such as Twitter or Instagram.

None of the three formats offered in this example works:

video/webm;codecs=vp9,opus
video/webm;codecs=vp8,opus
video/webm;codecs=h264,opus

I also tried video/mp4

Is there any format that will make my video work for this platforms? Can I do anything with javascript to fix the video before downloading it?