What is AVIF (AV1 Image File Format)?

How AVIF Works

AVIF (AV1 Image File Format) is one of the most efficient image formats available, and it works by borrowing from modern video. It stores a still image as a single keyframe encoded with the AV1 video codec, packaged inside the same ISO Base Media File Format container used by MP4. Structurally it is a close sibling of HEIC: both wrap a still image compressed with an advanced video codec, but where HEIC uses HEVC (H.265), AVIF uses AV1.

That difference is the whole reason AVIF matters. AV1 was developed by the Alliance for Open Media, a consortium including Google, Mozilla, Netflix, and others, specifically to be a high-efficiency codec that is open and royalty-free. So AVIF delivers compression on par with or better than HEIC, but without the patent-licensing problems that limit HEIC's support. It is, in effect, HEIC's quality with JPG's openness.

AVIF's efficiency is striking: it typically produces files significantly smaller than JPG at the same quality, often less than half the size, and frequently beats WebP too, especially at low bitrates. It also supports a wide feature set: lossy and lossless modes, transparency, wide color gamut and HDR, high bit depth, and even animation. For a web image, AVIF often achieves the smallest file of any widely-available format at a given quality.

Browser Support and Adoption

AVIF's adoption has grown quickly. It is now supported by Chrome, Firefox, and Safari, which covers the large majority of web users, and major platforms like Netflix and content delivery networks have embraced it for the bandwidth savings. Because it is royalty-free, there is no licensing barrier to building it into software and services, which has helped it spread faster than HEIC ever could on the open web.

The remaining caveats are practical. Support, while strong in browsers, is not yet as universal as JPG or PNG across all software, older tools, some email clients, and certain apps may not open AVIF. AVIF encoding can also be slower than JPG because AV1 compression is computationally heavy, though decoding (viewing) is fast. As with WebP, production sites typically serve AVIF with a JPG or WebP fallback for clients that cannot display it.

AVIF vs WebP vs JPG

For the best compression, AVIF usually wins: it produces the smallest files at a given quality, especially for photographs and at lower quality settings, and it handles HDR and wide color better than WebP. WebP has broader, slightly more mature support and faster encoding, making it a safe middle-ground upgrade over JPG. JPG remains the universal baseline that works absolutely everywhere. A common modern strategy is to serve AVIF first, fall back to WebP, then fall back to JPG, giving each visitor the smallest file their browser supports.

Should You Use AVIF?

For a performance-focused website, AVIF is worth adopting, with fallbacks, because the file-size savings are the largest available and it is open and royalty-free. For images that must work everywhere outside the browser, or in older software, JPG or PNG is still the safer choice. The practical approach mirrors WebP: keep a high-quality master, generate AVIF copies for web delivery, and provide a fallback so no visitor is left with a broken image. As browser and tool support continues to mature, AVIF is positioned to become the leading next-generation web image format.