What are AVIF and WebP files, and how to convert them

AVIF and WebP are modern image formats that websites use because they make smaller files than JPEG or PNG at a similar quality. To convert one, open it in Paint by Zaweba and use Save As to write a PNG or JPEG; to convert a whole folder at once, use File > Image Processor. Paint also saves AVIF and WebP, so the conversion works in the other direction too.

These formats often turn up when you save a picture from a web page and find that the program you wanted to use won't open it. Nothing is wrong with the file; it's just newer than some software.

What the two formats are

WebP came out of Google and is now supported by every major browser. It can be lossy, like JPEG, or lossless, like PNG, and it supports transparency and animation. For the web it's a handy all-rounder.

AVIF is newer still, based on the AV1 video codec. It usually squeezes photos even smaller than WebP while keeping them looking good, and it handles transparency and wider colour ranges. Support has spread quickly across browsers, but some older programs still can't read it.

Neither is a bad format. The only reason to convert is when you need to use the picture somewhere that expects a JPEG or PNG, such as an older program, a print service or a form that only accepts certain types.

Converting one picture

In Paint choose File > Open and select the AVIF or WebP file. It opens as an ordinary document. If you want to tidy it up first, crop or adjust it now. Then choose Save As. Pick JPEG for photos where a small file matters, or PNG when the picture has transparency, sharp text or flat colours that JPEG would blur. PNG can be saved at 16 bits too.

If the picture had a transparent background and you save as JPEG, the transparent parts get filled, because JPEG has no transparency. Choose PNG in that case.

Converting many at once

File > Image Processor takes a folder, or all the documents you have open, and converts every picture to JPEG, PNG, WebP or TIFF. You set the quality and can ask it to fit everything within a width and height, which is useful when you want the converted files smaller for email. It's the quickest way through a downloads folder full of WebP files.

Batch goes further. It runs a saved action over a folder, so you can resize, sharpen, add a border or remove a background as part of the conversion, with file name tokens such as the date and a batch-log.txt of what happened.

Going the other way

If you run a website, converting your own JPEGs to WebP or AVIF can make pages load faster. Paint saves both, and Image Processor will write WebP in bulk. Keep your originals in a lossless form, such as PNG or the .ptx working file, and treat the web copies as throwaway exports you can make again.

Picking quality settings

For JPEG, a high quality setting keeps photos looking like the original, while very low settings show blocky patches in skies and smooth areas. Converting from one lossy format to another loses a little each time, so convert once from the best copy you have rather than chaining conversions.

Paint by Zaweba is free software for Windows and works offline, so conversion happens on your own computer without uploading pictures to a converter website.