The short answer
- AVIF is an image format that stores AV1-coded still images or image sequences in a HEIF/ISOBMFF container, with support for lossy and lossless compression.
- Use an AVIF-capable image application, or use AOMedia's avifdec on Windows, macOS, or Linux. With avifdec, select the AVIF input and export JPEG, PNG, or YUV4MPEG2. Keep strict validation and resource limits enabled for untrusted files. On a phone, use an application that explicitly lists AVIF support; if none is available, convert the file on a supported desktop system.
- AVIF is not described as a scripting or executable format, but viewing it still parses a structured HEIF/ISOBMFF container and decodes AV1 data. Malformed or resource-intensive files can therefore present parser or resource-exhaustion risks. Open untrusted files with current libraries, strict validation, and bounded pixel and dimension limits.
AVIF file: what it is, how to open it, and how to convert it
AVIF was developed by the Alliance for Open Media. It can represent still images, image sequences, HDR, wide color gamut, monochrome and multichannel images, transparency, depth maps, multilayer images, and progressively decoded content. Its registered media type is image/avif. A conforming file identifies an avif still-image brand or avis image-sequence brand in its FileTypeBox; the brand need not occur at one fixed byte position.
AVIF supports both lossy and lossless compression. Converting AVIF to JPEG can discard transparency, higher bit depth, or other information: avifdec documents JPEG output as opaque and always 8 bits per channel. PNG output can be 8 or 16 bits and is the more suitable documented choice when transparency or higher bit depth must be retained.
How to open it
Use an AVIF-capable image application, or use AOMedia's avifdec on Windows, macOS, or Linux. With avifdec, select the AVIF input and export JPEG, PNG, or YUV4MPEG2. Keep strict validation and resource limits enabled for untrusted files. On a phone, use an application that explicitly lists AVIF support; if none is available, convert the file on a supported desktop system.
Use an AVIF-capable image application, or use AOMedia's avifdec on Windows, macOS, or Linux. With avifdec, select the AVIF input and export JPEG, PNG, or YUV4MPEG2. Keep strict validation and resource limits enabled for untrusted files. On a phone, use an application that explicitly lists AVIF support; if none is available, convert the file on a supported desktop system.
AVIF supports both lossy and lossless compression. Converting AVIF to JPEG can discard transparency, higher bit depth, or other information: avifdec documents JPEG output as opaque and always 8 bits per channel. PNG output can be 8 or 16 bits and is the more suitable documented choice when transparency or higher bit depth must be retained.
File safety
AVIF is not described as a scripting or executable format, but viewing it still parses a structured HEIF/ISOBMFF container and decodes AV1 data. Malformed or resource-intensive files can therefore present parser or resource-exhaustion risks. Open untrusted files with current libraries, strict validation, and bounded pixel and dimension limits.
An unknown sender, a name ending in two extensions, or contents that do not match the extension — check before you open it.
Converting it
AVIF supports both lossy and lossless compression. Converting AVIF to JPEG can discard transparency, higher bit depth, or other information: avifdec documents JPEG output as opaque and always 8 bits per channel. PNG output can be 8 or 16 bits and is the more suitable documented choice when transparency or higher bit depth must be retained.
Convert a copy, never the original, then compare quality, metadata, and layout against what you started with.
Common questions
What is an AVIF file format used for?
AVIF stores AV1-coded images in a HEIF container based on ISOBMFF. It can hold still images or sequences and supports features including HDR, wide color gamut, transparency, depth maps, multilayer images, and lossy or lossless compression.
How do I open an AVIF file?
Open it with an application that explicitly supports AVIF, or use AOMedia's avifdec. The official decoder can read AVIF and export JPEG, PNG, or YUV4MPEG2.
How do I open an AVIF file on Windows?
Install a documented Windows package of AOMedia's libavif and use avifdec to decode the file or export it as JPEG, PNG, or YUV4MPEG2.
How do I open an AVIF file on macOS?
Use a documented macOS package of libavif and run avifdec, or choose an image application that explicitly states it supports AVIF.
Why will an AVIF file not open?
The application may lack AVIF support, the file may be malformed, or validation and resource limits may reject its dimensions or total pixel count. Try a current avifdec build with strict validation and inspect the reported error.
What is the difference between AVIF and JPEG?
AVIF stores AV1-coded data in a HEIF/ISOBMFF container and supports features such as transparency, HDR, wide color gamut, sequences, and lossless compression. The documented avifdec JPEG output is opaque and limited to 8 bits per channel.
How do I convert an AVIF file to JPEG?
Use avifdec and select JPEG output. Expect possible information loss because its JPEG output is always 8 bits per channel and opaque.
How do I convert AVIF to PNG without losing transparency?
Use avifdec with PNG output. PNG output can be 8 or 16 bits, and unlike the documented JPEG output it can preserve transparency, subject to the source data and chosen decoding options.
Is an AVIF file safe to open?
AVIF is not described as executable or scripted, but decoding it exercises container parsers and AV1 codec libraries. Treat unknown files cautiously and use current software with strict validation and bounded resource limits.
Does an AVIF file have a fixed file signature?
No single fixed byte signature is asserted. A conforming file lists avif for a still image or avis for an image sequence in its FileTypeBox, and that identifier may be a compatible brand rather than the major brand.
How do I open an AVIF file on a phone?
Use a phone application that explicitly lists AVIF support. If no suitable application is available, convert the file on a supported desktop system before viewing it.
Related formats
Sources
AV1 Image File Format (AVIF), Version 1.2.0 · Alliance for Open Media official specification
IANA Registration: image/avif · Internet Assigned Numbers Authority
AOMediaCodec libavif · Alliance for Open Media official reference implementation repository
avifdec Manual · Alliance for Open Media official decoder documentation
Image File Type and Format Guide: AVIF · Mozilla Developer Network