MP4 vs WebM: which should you use?
A container comparison that comes down to where the video will be played.
MP4 wins on compatibility
MP4 with H.264 is the closest thing video has to a universal format. Every phone, browser, smart TV, editor and messaging app accepts it. If you are not sure where the file is going, this is the answer.
WebM wins on size for the web
WebM with VP9 typically produces a smaller file than H.264 at comparable quality, which matters if you are paying for bandwidth on your own site. Outside the browser, support drops off quickly — many editors and TVs will not open it.