Container literacy
HEIC, HEIF, and AVIF are related—but not interchangeable
These names mix a container family, coding formats, filename conventions, and compatibility brands. A trustworthy detector reports both the ISO BMFF container and the brand evidence instead of treating every ftyp box as HEIC.
The three terms
HEIF
High Efficiency Image File Format is a family of image containers built on ISO Base Media File Format. It can hold a primary image, thumbnails, auxiliary images, metadata, and sequences.
HEIC
HEIC is the common extension and compatibility label used for HEIF files containing HEVC-coded images, especially Apple camera photos. The container may still hold more than one item.
AVIF
AVIF uses the same container family with AV1 image coding. The avif brand identifies a still image profile; avis identifies an image sequence.
What the ftyp brands say
| Brand examples | Bounded interpretation | Important limit |
|---|---|---|
| heic, heix, heim, heis | HEVC-coded HEIF compatibility profiles | A brand does not prove every image item or metadata block is decodable. |
| mif1 | Generic HEIF image compatibility | The codec needs additional item properties; “HEIC” should not be guessed. |
| msf1 | HEIF image sequence compatibility | Timing and playback semantics require deeper parsing. |
| avif | AVIF still-image compatibility | Auxiliary alpha, HDR, and metadata behavior still need decoder support. |
| avis | AVIF image sequence | A converter must define whether it keeps animation or selects a frame. |
Why this matters during conversion
Orientation: a decoder may apply orientation while removing the original tag. Output pixels and output metadata must be checked separately.
Metadata: EXIF, GPS, capture dates, thumbnails, and maker notes are independent items or properties. Browser decoders commonly omit them from a newly encoded JPG or PNG.
Color and HDR: ICC, nclx color information, wide gamut, HDR transfer characteristics, and bit depth can be transformed or lost through browser canvas paths.
Multiple images: depth maps, bursts, sequences, and auxiliary images require an explicit selection policy. Silently taking the first decoded blob is not preservation.