Unless I'm mistaken, while AVIF may be "right around the corner", it's still quite a way off relative to the speed of technological advances. Unless I'm mistaken AV1 is very far from finalized or being a realistic option for the web, and as AVIF will effectively just be a still-image subset of AV1 it's going to take some time as well. (I'm still very excited about it, however.)

I suspect they might be motivated by the rapid way in which HEIF seems to be taking over. My understanding is that comparatively, the patent situation of WebP is much better. If you're a company concerned about software patents on the web, it might suddenly seem that throwing your weight behind WebP as a way of avoiding the proliferation of HEIF is worthwhile.

> Unless I'm mistaken AV1 is very far from finalized

AV1 is finalized: https://aomedia.org/av1-features/get-started/

I think there are a couple bugs and contradictions between the spec and reference implementation that are being ironed out, but the bitstream is now frozen.

The copy of Firefox that I'm using to type this has the AV1 library linked to it (via ffmpeg).

AV1 is enabled for video in the next release of Chrome, and the current release of Firefox has it behind a flag IIRC. The spec has been finalized since early this year, and the results are stunning: You can produce recognizable, sometimes perfectly passable, images at around one tenth of a bit per pixel.

Try the "clovisfest" test image here[0], with the most recent AV1 snapshot on the right, and MOZJPEG (the most advanced JPEG encoder on the market, AFAIK) on the left, with both set to the "Tiny" target bitrate (0.1bpp). Smooth, continuous grades look hideous on JPEG up to pretty high bitrates, and JPEG never quite reproduces hard edges or sharp specks properly; AV1 excels at both of these.

[0]: Image formats comparison <https://wyohknott.github.io/image-formats-comparison/#clovis...

Indeed, strange that Microsoft decided to support WebP and not wait for AVIF [1]. Mozilla had said that if at least one browser in addition to Chrome supports WebP, then they will consider supporting it, so looks like they are just fulfilling that promise [2].

WebP has its drawbacks, like no support for HDR content. AVIF supports it and Netflix would like to use it for video thumbnails.

[1] https://www.cnet.com/news/googles-webp-image-format-finally-...

[2] https://www.cnet.com/news/apple-ios-macos-tests-googles-webp...

We'll probably end up with both like we've had jpg and PNG, at least if more people/organizations call for it.

AVIF is primarily a lossy format, the place were WebP shines is in it's lossless mode. Being able to replace PNG as the de facto standard lossless format would yield better compression while still decoding and encoding faster.