>>46012861i'm sure there are a thousand ways to do it, but i got used to using a program called Boram back when i was making loads of kpop webms so I still use it
https://github.com/Kagami/boram/releasesto be 4chan compatible you have to disable the audio track in the 'audio fx' tab (if the board doesn't support audio webms), change the video codec to vp8 in the 'codecs' tab, and set the file size limit to whatever max the board supports. here it's 4mb iirc, on /mu/ it's 3mb.
so for screen captures in particular i just use OBS to record my desktop and then do the cropping (click and drag on the video preview)/trimming/resizing/encoding from that video to a 4chan webm in Boram
it's very easy and quick once you do it a time or two, it's not a complicated GUI desu
