What is an AVIF file? And where you can’t use one

The short version

• An AVIF (.avif) is a compressed picture, like a JPG but newer, and designed to be smaller.
• It opens in any current browser: Chrome, Edge, Firefox, Opera and Safari.
• Fine for: pictures on your website (Google Search lists AVIF) and eBay listings.
• Not for Google Merchant Center. AVIF isn’t on its list, and renaming the file to .jpg doesn’t help.
• Google Business Profile: Google’s photo guidelines say JPG or PNG. Use a JPG.
• Converting to JPG? Start from the original if you still have it. On our images, a JPG made from the AVIF was further from the original every time.
• Is it really smaller? On our 60 images, yes: smallest on every one, once the quality was matched. At the same quality number it looked bigger than WebP, and that comparison is misleading.

What is an AVIF file?

It is a picture format. Mozilla’s guide to image formats describes it like this: "AV1 Image File Format (AVIF) is a powerful, open source, royalty-free file format that encodes AV1 bitstreams in the High Efficiency Image File Format (HEIF) container." In plainer words: AV1 is a way of compressing video, which Mozilla says "was originally designed for video transmission over the Internet", and AVIF uses it to compress a single still picture.

If that container sounds familiar, it is the same one used by HEIC, the format iPhones can save their photos in. Microsoft’s developer documentation puts the two side by side: "HEIF files that are compressed with HEVC typically use the .heic file extension", and "HEIF files that use AV1 for compression typically use the .avif file extension." So an AVIF is a close cousin of the HEIC files we wrote about last week, with a different engine inside.

The format comes from the Alliance for Open Media, which calls it "an image format designed to offer superior image compression and quality compared to traditional formats" and says: "AVIF can provide over 50% file size savings compared to JPEG and over 30% savings compared to WebP." Those are its makers’ own figures. Our own test is further down.

If you saved a picture from a website and it arrived as .avif, that is simply the format the website sent to your browser.

Where AVIF works, and where it doesn’t

This is the part that matters if you sell things or run a website. We read each of these pages on 13 and 15 October 2026.

Merchant Center is the firm one. Its list is a requirement ("must point directly to a valid image file"), and AVIF isn’t on it. The same page closes the obvious shortcut: "The file extension must correspond to its actual format." Renaming photo.avif to photo.jpg doesn’t make it a JPG. Merchant Center has size rules too, which we covered in Google’s 500 × 500 image rule.

Business Profile is softer. Google introduces its list with "Your photos look best on Google if they meet the following standards", which reads like guidance rather than a list of what the upload will refuse. We haven’t tried uploading an AVIF to a Business Profile, so we can’t tell you it would be rejected. Google names JPG first, so use a JPG.

How to open an AVIF file

Open it with your web browser. Current versions of Chrome, Edge, Firefox, Opera and Safari all display AVIF; Mozilla’s guide lists the first version of each, in the table above.

On Windows, the photo apps may need a codec first. Microsoft’s developer documentation says the AV1 codec "might not be available on all PCs" and can be downloaded from the Microsoft Store. We haven’t tested this on a Windows PC ourselves, so if a photo app says it can’t open the file, the browser is the simpler route.

How to convert AVIF to JPG

First, go back to the original if you have it. Every time a picture is compressed, a little more of it is lost. We measured this: for each of our 60 test images, we made a JPG from the AVIF and another JPG straight from the original. The JPG made from the AVIF was further from the original on all 60. We found the same with HEIC. If the AVIF is all you have, convert it once and keep the JPG.

• On a Mac: Apple’s Preview guide says: "Open the file you want to convert, then choose File > Export." Then: "Click the Format pop-up menu, then choose HEIC, JPEG, JPEG-2000, OpenEXR, PDF, PNG or TIFF." Choose JPEG. Apple’s page doesn’t say which versions of Preview open AVIF, and we haven’t tested it.
• On Windows: open the picture in Paint and save it as a JPEG. Microsoft’s Paint page says "you can save your work in various file formats, including PNG, JPEG, BMP and GIF, among others". If Paint won’t open the AVIF, it may need the codec mentioned above. We haven’t tested Paint with an AVIF.
• Online converters: there are plenty. We haven’t tested any, and using one means uploading your picture to someone else’s server. That is fine for a product photo, but think twice for anything private.
• Don’t just rename it. Changing .avif to .jpg leaves an AVIF inside, and as Merchant Center’s rule shows, places that check will notice.

We added AVIF to our 60-image test

On 3 October we converted all 60 share images from this blog, each 1,200 × 630 pixels and each saved as a PNG, to JPG and to WebP, and published what we found in JPG or PNG?. For this post we ran the same 60 pictures again, with the same software and the same JPG and WebP settings, and added AVIF.

The first result was misleading. We saved each picture as AVIF at quality 85, the number we had used for JPG and WebP. The AVIFs came out about 41% bigger than the WebPs: 2.8 MB against 2.0 MB. That looks like a verdict, but it isn’t one. The AVIFs were also measurably closer to the original. Using PSNR, a standard measure of how far a compressed picture has drifted from the original (higher is closer), the typical AVIF scored 43.3 and the typical WebP 41.7. Each format’s quality number is its own scale. Quality 85 in one isn’t quality 85 in another, so comparing at the same number compares two different things.

So we matched the quality instead. For each picture, we found the smallest WebP and the smallest AVIF that were at least as close to the original as that picture’s JPG, measured by PSNR.

AVIF was the smallest on every one of the 60 pictures. Against WebP, its saving ranged from 6% to 47%, picture by picture.

We checked the result with a second measure, SSIM, which is meant to track what people notice rather than raw pixel differences. On SSIM, the AVIFs were level with the JPGs (typical score 0.977 against 0.978, above the JPG on 31 of the 60) and ahead of the WebPs on 54 of the 60. The WebPs scored a little below the JPGs on that measure (0.975), so matching on PSNR flatters WebP slightly. AVIF’s lead over WebP holds on both measures.

How does that compare with what the format’s makers claim? They say "over 50%" smaller than JPEG; we got about 61%. They say "over 30%" smaller than WebP; we got about 24%. On our pictures, by our measure, AVIF beat the makers’ JPEG figure and fell short of their WebP one.

What argues the other way

• Our test is small and particular. Our 60 pictures were generated by AI and are smooth and clean. Busy, grainy photos may compress differently. We used one piece of software (Pillow, a widely used image library) and its default AVIF speed setting. AVIF encoders have slower settings that we didn’t try, while for WebP we used the slowest, most thorough setting, as on 3 October.
• Other people’s figures differ from ours. Mozilla’s guide says "lossy AVIF images are around 50% smaller than JPEG images"; we got about 61%. Citing a third party’s comparison, it says AVIF generally compresses better than WebP: "median 50% vs. 30% compression for the same JPG set". That puts AVIF further ahead of WebP than we found. Those are different pictures and a different method from ours.
• Smaller isn’t the only thing. Mozilla’s guide notes: "AVIF does not support progressive rendering, so files must be fully downloaded before they can be displayed." It adds that this "often has little impact" because the files are smaller, but that for larger files it can matter.
• On your own website, AVIF may well be worth it. Google Search takes it and current browsers show it. Mozilla’s advice to web developers is that "you should include fallbacks to formats with better browser support", which is a job for whoever builds your site, not something to do by hand.
• We aren’t switching our own share images. They are JPGs because JPG is accepted almost everywhere. We haven’t checked whether the places that show them take AVIF.

Sources

• Mozilla (MDN): Image file type and format guide, for what AVIF is, browser versions, the fallback advice, progressive rendering and Mozilla’s size figures.
• Alliance for Open Media: What is AVIF?, for the makers’ own description and their 50% and 30% claims. The page carries no date.
• Google: Image SEO Best Practices (last updated 2 March 2026), Image link [image_link] (Merchant Center Help) and Manage your Business Profile photos and videos. eBay UK: Adding pictures to your listings.
• Microsoft: HEIF extension codec (developer documentation, last updated 29 January 2024) and Draw, Create and Edit with Paint. Apple: Convert image file types using Preview on Mac.
• All of the pages above were read on 13 and 15 October 2026.
• Our test: the same 60 share images as our 3 October test, run on 13 October 2026 with Pillow 12.2.0 (AVIF through libavif 1.4.1 and its aom encoder, at Pillow’s default speed). JPG at quality 85 with optimisation on; WebP at its slowest setting. PSNR was measured on the full colour picture; SSIM with ffmpeg. "Matched" means the smallest file whose PSNR was at least that picture’s JPG’s, found by searching the quality settings from 1 to 100. KB and MB mean thousands and millions of bytes.
• Every quotation above was tested automatically against the text of its source before publication.