What Is an AVIF File? (And How to Open One on Windows)

AVIF is the image format the web is currently moving to. It is smaller than JPEG, smaller than WebP, royalty-free — and almost nothing on a Windows desktop can open one, which is why you are reading this after saving a picture from a website.

The short answer

• AVIF stands for AV1 Image File Format.
• It is built on AV1, a deliberately royalty-free video codec.
• It is roughly half the size of a JPEG at comparable quality, and about 20–30% smaller than a WebP.
• Every current browser reads it. Almost no desktop software does.
• Windows needs Microsoft's free AV1 Video Extension just to preview one.

Why it exists

The short version is that the industry got tired of patents.

HEIC compresses beautifully and is built on HEVC, which is covered by patents held across several licensing pools with no single place to go and pay. That made HEVC expensive and legally awkward to ship, which is exactly why Windows does not include a HEIC decoder and why HEIC never spread beyond Apple.

So a consortium of large technology companies — the ones who would otherwise be paying those licences — built AV1 to be royalty-free from the start. AVIF is what you get when you use AV1 to compress a still image instead of a video.

The consequence is worth stating plainly: AVIF has no patent problem, so the adoption path that HEIC never got is open to it. Browsers picked it up quickly. Websites followed, because smaller images are directly cheaper. Desktop software is the part that has not caught up, and that is the gap you have just fallen into.

Why your PC still cannot open it

Two separate reasons, and it is worth knowing which one you are hitting.

Windows itself needs Microsoft's AV1 Video Extension from the Store to display AVIF in Photos and to show thumbnails in File Explorer. It is free, and it is not installed by default on most machines.

Your other software — the photo editor, the upload form, the print service, the document you are pasting into — mostly has no AVIF support whatsoever, and installing a Windows extension does nothing for any of it. AVIF is new enough that a great deal of perfectly current software has simply never been updated for it.

That second reason is the one that matters, and it is why the answer is usually to convert rather than to install anything.

AVIF against the alternatives

| | JPEG | WebP | AVIF | HEIC | |---|---|---|---|---| | Typical size | baseline | ~30% smaller | ~50% smaller | ~50% smaller | | Transparency | no | yes | yes | yes | | 10-bit colour | no | no | yes | yes | | Royalty-free | yes | yes | yes | no | | Opens everywhere | yes | mostly | rarely | rarely |

The pattern is consistent: newer formats are better at everything except being readable, and being readable is frequently the only property you actually need on a given afternoon.

What to convert it to

AVIF to JPG is the right default. It is the format nothing has refused since the mid-1990s, the files are small, and for a photograph the quality difference is invisible. If the image has a transparent background, JPG will flatten it to white.

AVIF to PNG is the right choice when the image has transparency — a logo, an icon, a graphic meant to sit over something else — or when you are about to edit it and want a lossless working copy.

Both conversions are one step, and both are worth doing in bulk if you have been saving images from the web for a while and have a folder full of files nothing will open.

Do it without uploading

The instinct is to search for an online AVIF converter, and they work. They also cap the file size, cap the number of files, and require you to hand over the image.

Converting on your own machine has neither cap, because there is no server to pay for. A decoder that runs locally also does not care whether Windows has the AV1 extension installed — it decodes AVIF itself, so conversion works on a machine that cannot even show you a thumbnail.

That last point is the practical one. You do not have to fix Windows to fix your files.