AVIF File Extensions and Official MIME Types

This article provides an overview of the officially assigned file extensions and MIME types for the AV1 Image File Format (AVIF). You will learn the exact specifications registered with the Internet Assigned Numbers Authority (IANA), the extensions used for both still and animated images, and how to identify them correctly in web environments.

Official MIME Types for AVIF

The official media type (MIME type) registered with IANA for AVIF is:

• image/avif

This is the primary MIME type used for standard, single-frame AVIF images.

For image sequences and animations (such as animated AVIF files), the following type is also recognized:

• image/avif-sequence

While image/avif-sequence exists for AV1 image sequences, the general standard and most web implementations accept image/avif for both still images and animated sequences to ensure broader compatibility across browsers.

Official File Extensions

AVIF files use two official extensions depending on the content:

• .avif: The standard extension for still AVIF images and the most common extension used across the web.
• .avifs: The official extension designated for AV1 Image Sequences (animated AVIF files).

Web Server Configuration

To ensure web browsers correctly serve and render AVIF files, servers must be configured to return the proper Content-Type header.

• Nginx (within the mime.types file):

  image/avif  avif;
  image/avif  avifs;

• Apache (within .htaccess or httpd.conf):

  AddType image/avif .avif
  AddType image/avif .avifs

Using .avif alongside image/avif provides complete compatibility with modern web browsers, content delivery networks (CDNs), and image processing pipelines.