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HEIF
What is a HEIF file?
The container standard behind HEIC. Same efficiency, same compatibility problems.
What HEIF is
HEIF is a container: a wrapper that holds streams encoded by something else. It stores a grid of pixels, so enlarging it past its own resolution softens it. It is used for phones and photography.
The extension is .heif, and the full name is High Efficiency Image File Format. Both matter less than what the file can hold, which is what the rest of this page is about.
Where HEIF came from
MPEG published it in 2015. The specification is ISO/IEC 23008-12.
Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.
The specification belongs to its vendor
Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.
Detail is traded for size
HEIF discards detail to stay small, and what it discards does not come back. That is the right trade for something being looked at and the wrong one for something being edited: each re-save takes another bite.
It can be transparent
HEIF carries an alpha channel, so a logo keeps its soft edges over whatever sits behind it instead of arriving in a white box.
It can hold more than one frame
HEIF can store an animation rather than a single still. That is worth knowing before converting one: a target that holds one frame keeps the first and drops the rest, usually without saying so.
Colour it can describe
Up to 10 bits per channel. It can work in YCbCr, the model video and JPEG compress in and wide-gamut colour.
More than eight bits per channel is what stops a gradient from stepping when it is edited, which is why it matters in a working file and rarely in a finished one.
It can hold several pages in one file
A HEIF file is not limited to one page, which matters when converting to something that is: a target that holds one image produces one file per page, and the numbering it chooses is worth checking before you send it on.
Opening it in a browser
Only some browsers read it.
Where support is uneven, serving a second format alongside it is the usual answer — the browser takes the one it understands and nobody is left out.
What it can carry besides the content
HEIF can hold EXIF, XMP, ICC profiles and GPS coordinates.
The GPS coordinates are the field worth thinking about before sending a file anywhere: they say where the photograph was taken, and almost nothing warns you that they are still in there.
It is a delivery format
HEIF is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.
What goes wrong with it
The recurring complaints: support outside its home ground is uneven.
None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.
The facts, in one place
| Extension | .heif |
|---|---|
| Media type | image/heif |
| Published by | MPEG |
| First published | 2015 |
| Specification | ISO/IEC 23008-12 |