File format

What is an AVIF file?

Checked against the sources on 13 November 2026Sizes measured 13 November 2026

In one paragraph

An AVIF file (AV1 Image File Format) stores images compressed with the AV1 video codec's still-image tools inside a HEIF container, the same ISO base media file structure HEIC uses. The Alliance for Open Media (AOMedia) publishes the specification; its v1.2.0 source is dated 16 October 2025. AVIF supports 8-, 10- and 12-bit images, transparency through an auxiliary alpha image, HDR and wide colour gamut, and image sequences for animation. The media type is image/avif.

AVIF at a glance

AVIF at a glance
Property	What the source says	Source
Media type	image/avif, registered with IANA on 28 January 2021 by the Alliance for Open Media.	IANA avif IANA
Container	A HEIF file (based on ISO BMFF) holding AV1 image items, with constraints taken from MIAF.	AVIF v1.2.0
Brands	A conforming file should include 'avif' (images) or 'avis' (image sequences) in its FileTypeBox; a file that claims one of the specification's profiles shall list one of them.	AVIF v1.2.0
Bit depth	AV1 supports 8, 10 and 12 bits; other depths are possible through sample-transform derived images.	AVIF v1.2.0
Transparency and HDR	Alpha is stored as an auxiliary AV1 image; HDR and wide colour gamut are supported alongside SDR.	AVIF v1.2.0
Largest image	A single AV1 coded image can reach 65536 x 65536. The Baseline profile caps one coded image at 8192 wide, 4352 high and 8,912,896 pixels; larger pictures are built from a grid of tiles.	AVIF v1.2.0
Progressive display	The specification supports progressive decoding through layered images. MDN states that AVIF does not support progressive rendering. Both statements are printed here as found.	AVIF v1.2.0 MDN
Browser support	MDN lists Chrome 85, Edge 121, Opera 71, Firefox 93 and Safari 16.1, with animated AVIF in Firefox from 113 (MDN read on 13 November 2026).	MDN

Each row was checked against the linked source on 13 November 2026.

A video codec's key frame, stored as a picture

AV1 was designed for video. AVIF reuses it for still pictures: the specification requires the data of an AV1 image item to be identical to an AV1 sample marked as a sync sample, the kind of frame a decoder can show without any other frame. The surrounding file is HEIF, the High Efficiency Image File Format, so an AVIF file is built from the same boxes as a HEIC file: a file-type box naming the brand, a meta box listing image items and their properties, and the coded data.

Because the container is shared, the extension and the brand matter more than the structure. The IANA registration for image/avif lists the extensions avif, heif, heifs and hif, and the specification asks AVIF files to declare the 'avif' or 'avis' brand so a reader can tell the items inside are AV1. A program that reads HEIC is not automatically able to read AVIF, because it still needs an AV1 decoder.

How to open an AVIF file

Open it in a current browser. MDN's guide lists support in Chrome, Edge, Firefox, Opera and Safari from the versions in the table above, and the Chromium build used for this page's measurements decoded the AVIF sample natively. That makes the browser the most reliable AVIF viewer on most computers.

If you need the image in a program that does not read AVIF, convert it to PNG to keep transparency and full detail, or to JPG for the widest compatibility. AltFTool's Image Converter decodes AVIF with the browser's own decoder and re-encodes it; the measured example shows what that produced for the sample file.

Why a browser can show AVIF but not always save it

Decoding and encoding are separate features. A browser that displays AVIF images does not necessarily let a web page create them. In the Chromium build measured here (version given below the table), asking the canvas for image/avif returned a PNG instead.

AltFTool's Image Converter tests the browser's AVIF encoder when it loads and disables the AVIF output, with a note, when there is none, so you are not handed a PNG renamed .avif. If your browser cannot encode AVIF, convert to WebP for a small web image, or use desktop software with an AV1 encoder when AVIF output specifically is required.

When AVIF is the right format

When AVIF is the right format
Your image	Use AVIF?	Why
Photo on a site with a <picture> fallback	Yes	Smaller than WebP at similar fidelity in the WebP vs AVIF measurement, with JPEG or WebP as the fallback.
HDR or 10-bit image for the web	Yes	AVIF carries 10- and 12-bit data and HDR signalling; JPEG's common form is 8-bit.
Image someone will open in older desktop software	No	Convert to JPG or PNG; older programs may lack an AV1 decoder.
Image you need to create in the browser	Check first	Some browsers display AVIF but cannot encode it from a page.
Very large panorama	With care	Beyond the Baseline profile limits the image must be tiled as a grid.
Upload form that lists only JPG	No	Convert first; the form will not accept it.

Measured example

The AVIF reference file, decoded by the browser and converted by the site's encoder
File	Bytes	Size	Fidelity to the original
Photo sample as AVIF (reference file, made outside the site)	57,992	56.6 KB	did not decode
Same AVIF converted to JPEG, quality 0.82	71,381	69.7 KB	35.1 dB
Same AVIF converted to WebP, quality 0.82	44,082	43.0 KB	34.9 dB
Canvas asked for image/avif from the photo (came back as image/png)	1,275,225	1245 KB	identical pixels

13 November 2026, Chromium 153.0.8010.12. Fidelity: PSNR against the original (higher is closer).

The reference AVIF of the photo is 56.6 KB. The browser decoded it natively, at 37.2 dB against the original pixels. Converted to JPEG at quality 0.82 it became 69.7 KB.

When the page asked the same browser's canvas for image/avif, it received image/png (1245.3 KB) instead: this Chromium build displays AVIF but does not encode it from a web page. That is why the reference file was made with libaom outside the site; how, and why at that setting, is listed under the samples below.

photo.avif was made outside the site with FFmpeg 6.1.1 (Ubuntu 7:6.1.1-3ubuntu5) with libaom-av1 3.8.2: still picture, crf 17, cpu-used 4, one thread, yuv420p; picked as the crf whose PSNR, decoded and measured with FFmpeg, came nearest the WebP 0.82 encode of the same sample.

How these files were made and measured

What this page does not claim

The AVIF facts here are read from the specification's source file (v1.2.0, dated 2025-10-16) in the AOMedia repository, not from the published HTML copy.
HEIF (ISO/IEC 23008-12) and MIAF (ISO/IEC 23000-22) themselves were not opened; nothing on this page depends on wording from them.

Questions

Is AVIF the same as HEIC?

No, though they share a container. Both are HEIF files, but AVIF's images are coded with AV1 and HEIC's with HEVC (H.265). A reader needs the matching decoder, so support for one does not imply support for the other.

Does AVIF support transparency?

Yes. The AVIF specification stores alpha as an auxiliary AV1 image linked to the main one, so a lossy AVIF can have a transparent background.

Which browsers open AVIF files?

MDN's guide, read on 13 November 2026, lists Chrome 85, Edge 121, Opera 71, Firefox 93 and Safari 16.1 as the first versions with support, and Firefox 113 for animated AVIF.

Why does saving as AVIF give me a PNG?

Because the browser can decode AVIF but cannot encode it from a web page. The Chromium build measured for this page returned a PNG when asked for AVIF. Use WebP instead, or software that includes an AV1 encoder.

Can AVIF be animated?

Yes. AVIF defines AV1 image sequences, signalled with the 'avis' brand, which is how animated AVIF files are built.

Sources

Working with a AVIF file?

Turn an AVIF into JPG, PNG or WebP; it also writes AVIF where your browser can encode it. The Image Converter runs in your browser tab, with no account.

Open the Image Converter