What is the AVIFS file format?
An .avifs file is an animated image made from a sequence of AVIF frames. It comes from the Alliance for Open Media, the group behind the AV1 codec, and it is the moving-image counterpart to the still .avif format. Rather than reuse one extension for both still and animated pictures, as .gif and .webp do, AVIF splits them so you can tell at a glance whether an image moves.
Under the hood, an .avifs file is an ISO Base Media File Format container, the same box structure used by MP4 and HEIF. A short ftyp header near the start declares the avis brand, which marks the file as a sequence instead of a single image. The frames sit in a track that carries the timing, and each frame is an independently coded AV1 keyframe. That means animated AVIF acts like a timed series of full pictures rather than a true video with motion prediction. The format keeps AVIF's strengths: 8 to 12-bit color, alpha transparency, and HDR.
Security & safety
RISK: LOWAVIFS is a container for image data and holds no scripts or executable code. The main practical concern is decoder bugs in older libavif or media libraries, so keep viewers up to date. Files from unknown sources are safe to open in a current browser.
Format details
in a nutshellFULL NAMEAVIF Image Sequenceaka Animated AVIF, AV1 Image Sequence
DEVELOPERAlliance for Open Mediasince 2019
CATEGORYRaster Image Files
MIME TYPEimage/avif
TYPEBinary container (ISO Base Media File Format)
STANDARDOpen · royalty-free
MAGIC BYTES · FILE SIGNATURE
OFFSET
04
HEX
66 74 79 70
ASCII
·
Starts with an ISOBMFF FileTypeBox. Bytes 4-7 are 'ftyp'. An image sequence is identified by the brand 'avis' (ASCII 61 76 69 73) appearing as the major_brand or in compatible_brands, rather than the still-image brand 'avif'. There is no fixed signature at offset 0.
Programs that open AVIFS files
Windows4 apps
Mozilla Firefox
Open-source Open the file in a tab to play it; Firefox added animated AVIF support in version 114. 
Google Chrome
Free Drag the .avifs file into a browser tab to view the animation natively; Chrome has supported animated AVIF since version 93. 
qView
Open-source Open the .avifs file directly in this lightweight image viewer to play the animation frame by frame.
libavif (avifdec)
Open-source Use the reference avifdec command-line tool to decode frames from the sequence for inspection or extraction. 
macOS3 apps
Safari
Built-in Open the file in a tab; Safari plays animated AVIF starting with version 17 on macOS Sonoma and later.
libavif (avifdec)
Open-source Install via Homebrew and use avifdec to decode the sequence from the terminal. 
Linux3 apps
FFmpeg
Open-source Decode or re-encode the sequence with ffmpeg -i input.avifs ... since FFmpeg reads AV1 in ISOBMFF.
libavif (avifdec)
Open-source Use avifdec to decode individual frames, or view the file in a Chromium/Firefox build. 
Android1 app
Google Chrome
Free Open the file in the browser; Android 12 and later also decode AVIF at the OS level.
iOS1 app
Web1 app
ezgif Animated AVIF tool
Free Upload an .avifs file to view, split into frames, or convert it in the browser. Technical details
deep spec| Encoding | AV1 (AOMedia Video 1) intra-coded frames |
| Byte order | Big-endian (ISOBMFF box sizes and fields) |
| Container | ISO Base Media File Format (ISOBMFF), the same MP4/HEIF box structure |
| Compression | Lossy or lossless AV1; each frame is an independently coded AV1 sample |
| Encryption | Not part of the base format |
| Typical size | Frame-count dependent; commonly a fraction of an equivalent animated GIF or WebP |
| Structure | A FileTypeBox (ftyp) declaring the 'avis' brand, followed by a Movie Box (moov) containing an image-sequence track. The track uses the 'pict' handler and one sample description entry; timing is carried by the container, so playback order and per-frame duration are defined by the track rather than the codec. |
| Integrity | None built in beyond ISOBMFF box length fields |
| Platforms | Windows, macOS, Linux, Android, iOS |
| Color depth | 8, 10, and 12-bit |
| Hdr Support | Yes (PQ and HLG transfer characteristics) |
| Transparency | Yes (alpha channel) |
| Notes | Built as a conformant MIAF/HEIF image sequence. The MIAF AV1 baseline profile is identified by the brand MA1B and the advanced profile by MA1A. The 'avio' brand may be present when the sequence contains only intra-frame samples. Distinct from a real AV1 video: frames are keyframes with no inter-frame prediction in the still-image sequence profile. |
| Released | 2019 |
| Latest version | AVIF v1.2.0 (2025) |
| Open standard | Yes · royalty-free |
| Specification | aomediacodec.github.io |
AVIFS conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about AVIFS files.
Frequently asked questions
What is the difference between .avif and .avifs?
.avif holds a single still image, while .avifs holds an animated sequence of AVIF frames. The Alliance for Open Media chose separate extensions so you can tell a moving image from a static one before opening it. Internally the sequence uses the avis brand instead of avif.How do I open an .avifs file?
The simplest way is to drag it into a current web browser such as Chrome, Firefox, Edge, or Safari, all of which play animated AVIF. On the desktop, qView opens the file and lets you step through frames.
Why won't my .avifs file open in Photoshop or the default viewer?
Many image editors and older OS previewers only handle still
.avif, not the animated sequence. Use a browser or qView, or convert the file to .gif or .webp first with FFmpeg or ezgif.Can I convert an .avifs to a GIF?
Yes. Upload it to ezgif or run FFmpeg to produce an animated
.gif. Expect a larger file and reduced color depth, since GIF is limited to 256 colors per frame.Is an .avifs file basically a video?
Not quite. It is stored in the same ISOBMFF container as MP4, but in the still-image sequence profile every frame is a keyframe with no motion prediction, so it behaves like a timed slideshow of independent pictures.
Are .avifs files smaller than animated GIFs?
Usually by a wide margin. AV1 compression often cuts an animation to a fraction of the equivalent GIF size while supporting more colors, transparency, and HDR.
References
1AVIF - Wikipediaen.wikipedia.org
2AV1 Image File Format (AVIF) specification v1.1.0 - Alliance for Open Mediaaomediacodec.github.io
