AVIF converter
AVIF is the most efficient still-image format in general use and the one your software is most likely to refuse. This page converts in both directions, locally, with the reference AV1 encoder running in your browser — and explains what the format is actually good at, which decides whether converting to it is worth doing at all.
What AVIF is
AVIF stores a still image using the AV1 video codec's intra-frame compression, wrapped in the same container family as MP4. That inheritance is where its advantages come from: AV1 was designed a decade after the codecs behind JPEG and WebP, with far more computing power assumed at both ends.
In practice that means files roughly half the size of an equivalent JPEG, noticeably better handling of gradients and dark areas — the places JPEG bands and blocks first — a full alpha channel, and support for higher bit depths and wide colour gamuts.
The cost is encoding time. AV1 encoding is expensive, and running it in a browser tab means several seconds per image where WebP takes a fraction of one.
When converting to AVIF is worth it
Photographs on a website you control, where you can serve AVIF with a fallback: clearly worth it, and the biggest saving available.
Large photo libraries where storage costs money: worth it, provided you are certain you will not need the original quality back, because the conversion is lossy.
Small icons, flat artwork and anything under a few kilobytes: usually not. AVIF's container overhead is not amortised at that size and PNG frequently wins outright.
Anything that has to open in arbitrary software: no. Convert away from AVIF instead.
How the browser support works here
Decoding uses your browser's own AVIF support where it exists, which is faster and lighter on memory than anything that could be shipped to the page. Where it does not exist, a decoder is loaded on demand so the conversion still works.
Encoding always uses a bundled build of libaom, because no browser will encode AVIF from a canvas. It is fetched only when AVIF output is actually requested, which is why the page itself loads quickly.
AVIF conversions
Questions
Why will my AVIF not open in Photoshop or Windows Photo Viewer?
Support outside browsers is still patchy. Recent Photoshop versions handle it, older ones do not, and Windows needs the AV1 Video Extension installed. Converting to PNG or JPG is the reliable answer.
Is AVIF lossless?
The format defines a lossless mode, but the encoder used here is always lossy, including at quality 100. If you need an exact copy, use PNG.
Does AVIF support transparency and animation?
Both. Transparency is fully supported here. Animated AVIF files are read for their first image only — animation is not carried across.