Who can help me please ?
I want to show video captures, but even when I capture 30 seconds, the video size is at least 200MB. How can I reduce the size ? I could lower the quality, but it would be horrible and we wouldn't see anything. The maximum size allowed here is 4MB.
How can I magically upload a 30-second video that was 200MB to a maximum of 4mb ?

You could either dial down your capture software settings to try to get a smaller mp4, or convert your current file using ffmpeg

>>213184062
Software names ?

>>213184084
If you're comfortable with cmd you can use ffmpeg directly, otherwise use stuff like handbrake that at least has a GUI

>>213184084
Avidemux, allows you to set the video&audio Bitrate/códec.

>>213183999 (OP)
Convert them into webm and turn the sound off so you may be able to post it here.
https://www.freeconvert.com/webm-converter