What's the difference between WebP and AVIF?
1 min read · Last updated June 2026
Both are modern image formats that are much smaller than JPEG or PNG at the same quality. AVIF is the newer of the two and usually produces the smallest files; WebP has been around longer and is supported by virtually every current browser. You do not have to choose - SlashImage makes both, and each visitor's browser picks the one it can use.
When each one wins
- AVIF usually wins on size, especially for photographs, where it can be noticeably smaller than WebP. Every current major browser supports AVIF now; the gap is limited to older devices that have never updated.
- WebP is a little larger than AVIF but is supported almost everywhere, so it is the reliable choice for browsers that don't do AVIF.
You can use both
By default SlashImage generates both a WebP and an AVIF copy of each image (the Generate WebP and Generate AVIF toggles under Output Formats). Delivery lists AVIF first, then WebP, then your optimized JPEG or PNG, and the browser downloads the first one it understands. So a recent browser gets the tiny AVIF, a slightly older one gets the WebP, and the oldest still gets a working image. There is no downside to leaving both on. For how that handoff works, see How does WebP and AVIF delivery work?.
Browser support
WebP is supported in every current browser. AVIF is supported in every current major browser too, with only a few niche exceptions like Opera Mini and QQ Browser. Any browser that can't display them automatically receives your optimized JPEG or PNG. For the live picture, see caniuse.com/webp and caniuse.com/avif.