It looks like normal <video> tags that attempt to load webm, then mp4, then falls back on a still image. All assets are loaded from their own webserver too (also my PiHole didn't block anything.)
Perhaps you have autoplay blocked? They are set to autoplay by the looks of things.
Re:Runway – Create impossible video
by randallsquared on Wednesday July 07, 2021 @09:56PM
(#27767752)
I do indeed have autoplay blocked, but I would expect controls to appear if something could be played. Maybe the weirdest part of this personal revelation is that it hasn't happened more often (that I know of).
Those videos or GIFs or whatever they are work fine in Chrome and Safari, so it turned out that I was missing something. :)