Why convert WebP to AVIF
WebP was the format that made images on the web noticeably lighter. AVIF is the next step: it is built on the compression of the AV1 video codec and usually stores the same picture in fewer bytes than WebP at a similar visual quality. For a site that already serves WebP, switching the heaviest images to AVIF is one of the few remaining ways to cut page weight without visibly changing anything.
Expect a smaller gain than you would get converting from JPG, though. WebP is already efficient, so there is less left to squeeze out, and the result depends a lot on the image — smooth gradients and soft backgrounds shrink the most, noisy or highly detailed photos the least. Every result shows its size change, so you can tell immediately whether a particular file was worth converting.
The one real caveat: lossy to lossy
Most WebP images on the web are lossy. Re-encoding a lossy image into another lossy format adds a little more loss on top of what is already there, much like re-saving a JPG. It is usually invisible at the High setting, but if you still have the original file, start from that instead — use the JPG to AVIF or PNG to AVIF converter. Lossless WebP files, common for screenshots, logos and interface graphics, don't have this problem.
Transparency and animation
AVIF has a full alpha channel, so transparent and partly transparent areas of a WebP carry over as they are. Animated WebP files are a different story: this tool converts the first frame and produces a still AVIF image, so it is the wrong choice if you need to keep the animation.
Choosing a quality setting
| Setting | When to use it |
|---|---|
| Maximum (95%) | Lossless WebP sources, or images where fine detail matters |
| High (85%) | The sensible default for most images |
| Medium (75%) | Large hero images where page speed matters most |
| Small file (60%) | Thumbnails and previews shown at small sizes |
How the AVIF encoding works
Every current browser can display AVIF, but none of the major ones can create AVIF files on its own. So the first time you convert, this tool loads an open-source AVIF encoder — libavif, compiled to WebAssembly. It is a one-time download of a few megabytes that your browser then keeps cached, and it runs in a background thread, so the page stays responsive while a batch encodes. AVIF is slower to encode than WebP; a large photo can take a few seconds.
Where AVIF works
Chrome, Edge, Firefox and Safari 16 or later all display AVIF, which covers the vast majority of visitors to a website. Older image editors, some phone galleries and a few upload forms still don't accept it, so keep the WebP copy if a file has to work in software you don't control.
Nothing leaves your device. The WebP is decoded and re-encoded as AVIF entirely inside your browser, with no account, no watermark and no limit on the number of files.