Progressive AVIF is very flexible: it supports up to four passes, at configurable quality and dimension scaling levels. You can have any given pass reference up to two previous ones for refinement (thanks to AV1's strong inter-encoding capabilities), and you add filters to non-final passes (like blurring) to achieve a desired loading aesthetic.

That JXL page happens to use two passes, but the knobs are there to customize the experience to fit the use case.

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janwas an hour ago | parent [-]

I find it misleading to call AVIF's "up to four passes" "very flexible".

It seems quite limited compared to the JPEG XL ability to truncate the bitstream anywhere, or send the progressive updates for salient regions first [1].

[1]: https://opensource.googleblog.com/2021/09/using-saliency-in-...

	▲	jaffathecake 41 minutes ago \| parent [-]
		I don't think the truncation thing is beneficial to the web. By the time the browser would terminate the connection, it has likely downloaded way more than it needs https://jakearchibald.com/2025/present-and-future-of-progres...