image/avif

An AV1 video keyframe dressed up as an image, wrapped in the same ISO-BMFF box structure as HEIF and MP4. Send it for photographic content where it beats JPEG and WebP on size at the same quality, but negotiate via the Accept header rather than serving it unconditionally — encode times are long and older clients still lack decoders. Like every ISO-BMFF format, identification lives in the ftyp box at offset 4, not at the start of the file; the brand avif marks a still image, avis an image sequence.

Defined by AV1 Image File Format (AVIF) · IANA registration. Registry facts from the IANA media-types registry via mime-db.