Video Poster Without Poster Attribute (mobile Browsers)

I am using video HTML tag. So far, if I am NOT specifying any poster, how one will be selected? Does it depend on video file format? Does it depend on video content (first frame et

Solution 1:

So far I've only ever used MP4 files with the video tag and each time I've not specified a poster image. It has picked up the first frame by default.

I know this information doesn't have any concrete evidence for you and may not help but thought I would share my experience.