What can your browser decode?
Support tables tell you about browsers in general. This page probes the one you are using right now: real decode attempts, real capability queries, on your actual hardware.
Probing your browser's decoders…
Why answers differ machine to machine
Codec support is not just a browser-version question. HEVC in Chrome, Edge and Firefox is delegated to whatever decoder your OS and GPU provide, so the same browser answers differently on different laptops. AV1 on Apple devices depends on the hardware generation. And MediaCapabilities' "power efficient" flag is really asking whether a hardware decoder exists, which is the difference between video that sips battery and video that drains it.
This is why production players never hardcode a codec: they ask, then
pick. The same negotiation happens in every
<video> element with multiple sources, in every
DASH/HLS manifest, and in this site's own
AV1 comparison.