AVIF

What it is

AVIF stores still images using the intra-frame coding of AV1, a royalty-free video codec. Video codecs have had far more engineering attention than still-image codecs over the last decade, and AVIF inherits all of it: better prediction, larger and more flexible block partitioning, and better handling of smooth areas than a format designed in 1992.

It supports lossy and lossless modes, an alpha channel, high bit depths and wide colour gamuts. Every current major browser decodes it.

What it is genuinely better at

Gradients and flat colour, by a wide margin. A sky that bands visibly as an 80-quality JPEG can be clean as an AVIF at half the file size. This is the single most visible difference in ordinary use, because banding is the artefact people notice without knowing what it is called.

It also holds together at bitrates where JPEG has fallen apart, which makes it the right choice when a large image must be small — a full-width hero, a background photograph, anything where the file is measured in hundreds of kilobytes rather than tens.

What it costs

Encode time. Depending on the effort setting, AVIF encoding can take ten to fifty times longer than JPEG for the same image. On one hero image that is irrelevant; on two hundred product photos it is the difference between a coffee and an afternoon. This single fact decides most real choices between AVIF and WebP.

Small images barely benefit. AVIF carries more container overhead than JPEG, so below roughly 10 KB — icons, tiny thumbnails, avatars — the fixed costs eat the compression advantage and a WebP or even a PNG can come out smaller. AVIF's advantage grows with image size.

Support is good in browsers and patchy everywhere else. Older installed browser versions, some in-app browsers and most non-browser software do not decode it. If your delivery path can serve a fallback this is a non-issue; if it cannot, it is a hard blocker.

When to reach for it

One or a few large, prominent images where the encode cost is paid once and the bandwidth saving is paid on every view. For batches, for small images, and for anything that has to open outside a browser, WebP or JPEG remains the better answer.