People have asked for extended capabilities of HTML videos, this Gist is used to showcase a somewhat niched use case that incorporates theoretical capabilities as suggested in the issues raised by others, as mentioned below.
Use case:
Autoplay a background-video only on screens larger than 1000px (where the user hasn't set a preference to reduce motion),
if the user prefers reduced motion and/or is on a smaller device then show the poster image instead.
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<video autoplay muted playsinline>