This release does add AV1 support, just only for devices with hardware decoding support [1]. I’m not entirely sure that restriction applies to desktop as well as mobile, it doesn’t work on my Mac without hardware support even after enabling the disabled feature flags, but I only upgraded Safari, not macOS.

Hardware-only is the right move IMO. Literally earlier today I was dealing with stuttering video that turned out to be caused by Chrome putting me on a software implementation of a “better” codec. These new codecs are only better on devices that can run them without stuttering, heating up, and chewing through battery.

[1]: https://webkit.org/blog/14445/webkit-features-in-safari-17-0...