WebP already compresses images well, and AVIF goes a step further. For many photographs an AVIF is somewhat smaller than a WebP of similar visual quality, often by 10 to 30 percent, and it also keeps transparency. That is why websites that already use WebP sometimes move to AVIF for their largest images.
Both formats are lossy, so converting from one to the other adds a second round of compression. Start from the best-quality WebP you have, and do not convert the same image back and forth. AVIF is also less widely supported: current versions of Chrome, Firefox, Safari and Edge open it, but older browsers and some apps do not, and WebP has been supported for longer. Animated WebP files become a single still image, and encoding runs in your browser, so large images take a few seconds each.
Choose High for a good balance, Max for the least visible loss, or Low when file size matters most. The pixel dimensions never change, each file keeps its name with only the extension swapped, and no metadata or watermark is added. Everything runs in your browser, so your images are never uploaded.
Tip: if the AVIF comes out about the same size as the WebP, keep the WebP. It opens in more places.
Often, but not always. For photographs it is commonly 10 to 30 percent smaller at similar visual quality. For flat graphics the difference can be small.
Slightly. Both are lossy formats, so the conversion adds a little more loss. At High quality it is hard to notice.
Yes. Transparent areas of your WebP stay transparent in the AVIF.
Only a single still image is produced, not an animation.
Yes. Add them all, convert once and download a single ZIP. Only the extension changes. A file named holiday.webp becomes holiday.avif.
No. The conversion happens in your browser and the files never leave your device.