What Is AVIF, and Why Won't Some Programs Open These Files?

Meeting a new file extension

You right-clicked an image, saved it, and got a .avif file. Or perhaps a designer sent you a file with that extension. You double-clicked it and your computer had no idea what to do.

AVIF is an image format that has spread rapidly across the web in recent years. Technically it is quite impressive; in practice it does not yet work everywhere. In this article we explain what the format is, why it is so efficient, and why some programs cannot cope with it.

What is AVIF?

AVIF stands for AV1 Image File Format. As the name suggests, the format is derived from a video codec called AV1.

The logic runs like this: modern video codecs have highly advanced techniques, developed over years, for storing a single frame with as little data as possible. In video this is called intra-frame coding — compressing a frame entirely on its own, without looking at neighbouring frames. A photograph is, after all, a single frame. So if you take the video world's best intra-frame coding and package it as an image format, you get a very efficient photo format.

That is exactly what AVIF is: the AV1 codec's intra-frame coding, placed inside an image file container.

Why is it so small?

JPG is a standard defined in the early 1990s and designed for the computing power of the day. It divides the image into fixed-size blocks and, within each block, discards the frequency components the eye barely notices. Ingenious for its time, crude by today's standards.

AV1-based encoding is far more flexible. It can divide the image into variable-sized regions, using large blocks in flat areas and shrinking them in detailed ones, and it can try far more directions and methods to predict a region's content from its neighbours. In short, it searches for the "cheapest way to describe" each image from a far wider pool of options.

The result is a widely reported observation: at the same visual quality, AVIF is generally significantly smaller than JPG — the frequently quoted figure of roughly half is an approximation, and the real ratio varies considerably with the image's content. The gain is large in images with flat colour areas and smooth gradients; the difference narrows in photographs with heavy noise and fine texture.

AVIF is generally more efficient than WEBP too, though the gap there is far smaller than against JPG.

The other things JPG cannot do

Size is not AVIF's only advantage. The format also supports several features JPG has never been able to carry:

• Alpha channel (transparency). It can hold transparent and semi-transparent areas, like PNG.
• High bit depth. 10 and 12 bits per channel are supported; JPG is limited to 8. This reduces banding in smooth sky gradients.
• Wide colour gamut and HDR. It can carry the wider colour range modern displays are capable of showing.
• Both lossy and lossless modes. It can be saved either way as needed; in lossless mode most of the size advantage is given up.

So why won't some programs open it?

The issue here is not the format's quality but its age.

For a piece of software to display an AVIF file, it has to contain an AV1 decoder. That means the software has to have been updated. And most software in the world does not get updated.

The places that cause problems in practice are these:

• Old desktop programs. Photoshop before a certain version, old image viewers and free tools that have not been maintained in years do not recognise AVIF.
• Old operating systems. On older Windows and mobile versions without system-level image decoder support, the file does not even appear in previews.
• Old phones. Devices that have gone a long time without updates may be unable to open the file.
• Content management and e-commerce platforms. Many dashboards check file types against a whitelist during upload, and AVIF may not be on that list.
• Office software and presentation tools. Dragging an AVIF straight onto a slide often does not work.
• Messaging and social platforms. Some reject the file, some accept it and convert it to their own format.

Current mainstream web browsers, on the other hand, do support AVIF. This produces an odd situation: the file opens beautifully in a browser but will not open on the desktop. It does not mean your file is corrupt.

The cost of encoding

Another practical drawback of AVIF is that producing it is computationally expensive. Because the encoder evaluates far more options, converting an image to AVIF takes noticeably longer than converting the same image to JPG. For a single file this difference is trivial; if you are batch-converting an archive of thousands of images, it is a cost you need to plan for.

What should you do?

If the AVIF in your hands will not open, you have two options. The first is to update the software you are trying to open it with. The second, and usually more practical, is to convert the file to a widespread format.

If the content is photographic and there is no transparency, converting the AVIF to JPG gives the most compatible result. If the image has transparent areas or is a sharp-edged graphic, PNG is the better target.

If you are producing AVIF for your own website and addressing a broad, unfamiliar audience, it is still wise to keep a JPG fallback alongside it. HTML's picture element exists for exactly this: the browser downloads the AVIF if it supports it and the JPG if it does not.

In summary

AVIF is a next-generation standard that brings the best techniques of the video compression world into a photo format. It is considerably smaller than JPG at the same quality and supports transparency and high colour depth. Its weakness is not technical but ecosystemic: most of the software world does not recognise it yet. So using AVIF on the web makes sense, but when you need to send the file to someone or open it in a program, converting is usually the fastest route.