# Glossary of HEIC and image format terms

> Short, precise definitions of the terms used across this site, in the sense they actually carry when you are dealing with iPhone photos.

Source: https://jpg-heic.com/glossary | Section:  | Updated: 2026-08-31

Terms are defined here in the sense they carry in practice, not the broadest possible sense.
 Where a distinction causes real confusion, the definition says so.

**HEIC**
High Efficiency Image Container. Apple's file extension for a HEIF file whose image is compressed with HEVC. Default photo format on iPhone and iPad since iOS 11.

**HEIF**
High Efficiency Image File Format, ISO/IEC 23008-12. The container standard itself, which can hold images compressed by several different codecs.

**HEVC**
High Efficiency Video Coding, also called H.265. The codec that compresses the image inside a HEIC file. Patent-licensed, which is why support is uneven.

**HIF**
Canon's file extension for HEIF images from EOS R series cameras. The same container as HEIC, usually holding 10-bit data.

**AVIF**
AV1 Image File Format. Uses the HEIF container design with the royalty-free AV1 codec instead of HEVC, which is why browsers support it and HEIC never got support.

**JPEG**
The 1992 image standard behind .jpg and .jpeg files. Lossy, 8-bit, no transparency, and readable by effectively every device made since.

**Lossy compression**
Compression that permanently discards image information judged least noticeable. JPEG, HEIC, WebP and AVIF are all lossy by default.

**Lossless compression**
Compression that reproduces the original pixels exactly. PNG is always lossless; WebP and HEIC each have an optional lossless mode.

**EXIF**
Exchangeable Image File Format. The metadata block carrying camera model, exposure settings, capture time and, often, GPS coordinates.

**Display P3**
A wide colour space used by recent iPhones, roughly 25% larger than sRGB. Converting to sRGB without translating the values is what makes photos look flat.

**sRGB**
The standard colour space of the web. The safe target for anything shared, uploaded or printed.

**Alpha channel**
Per-pixel transparency data. Supported by PNG, WebP, AVIF and HEIC, but not by JPEG, which fills transparent areas with white.

**Orientation flag**
An EXIF value from 1 to 8 telling software how to rotate a photo before display. Ignoring it is why converted photos come out sideways.

**Live Photo**
An iPhone capture stored as two files: a HEIC still and a short MOV video. Image converters only ever see the still.

**Depth map**
An auxiliary image recording distance from the lens, stored alongside the photo in a HEIC container and used for Portrait mode blur.

**libheif**
The open-source reference decoder for HEIF and HEIC. Compiled to WebAssembly, it is what lets a browser read HEIC without any system codec.

**WebAssembly**
A binary format that runs compiled code at near-native speed inside a browser tab. It is what makes local, upload-free conversion possible.

**HEVC Video Extensions**
The Microsoft Store package that lets Windows decode HEIC. Paid, though a free device-manufacturer version exists for many PCs.

**Container format**
A file structure that holds one or more compressed images plus metadata. HEIF is a container; HEVC is the codec used inside it.

**Chroma subsampling**
Storing colour detail at lower resolution than brightness detail, since the eye is less sensitive to it. Used by JPEG and HEIC alike.

## The three confusions worth clearing up

 - **HEIC is not a codec.** It is a file extension. The codec inside is HEVC, and the
 container is HEIF. Software that says it cannot open HEIC usually means it has no HEVC decoder.

 - **AVIF is not HEIC.** They share a container design but use different codecs, which is why
 one works in browsers and the other does not.

 - **Lossless does not mean better.** Converting an already-lossy HEIC to PNG preserves what
 is there and prevents further loss. It cannot recover what the original encoder discarded.

## Frequently asked questions

**What is the difference between HEIC and HEVC?**

HEIC is the file extension and HEIF is the container standard. HEVC is the codec that compresses the picture stored inside that container.

**Is AVIF the same as HEIC?**

No. The two formats are cousins rather than twins: AVIF borrows the container layout but swaps HEVC for AV1, which is why browsers read one and not the other.

**What does lossy mean for my photos?**

Information is permanently discarded during compression to make the file smaller. It is invisible at high quality settings and becomes obvious as the setting drops.