HEIC / HEIF (High Efficiency Image File Format)

HEIF is a container for images, built on the ISO base media file format (the box structure of MP4). HEIC is HEIF whose images are coded with HEVC (H.265), the video codec used for 4K video. It’s the default photo format on iPhones and iPads (since iOS 11) and on many Android phones, Canon and Sony cameras. At the same quality a HEIC photo is about half the size of a JPEG, and it can store 10-bit color, HDR, transparency, depth maps, live photo sequences and several images in one file.

The same container also holds other codecs: AVIF is HEIF with AV1, and there are brands for JPEG, AVC (H.264), VVC (H.266) and uncompressed images. This page covers HEVC-coded files, the .heic files phones produce.

When to use HEIC#

• Use when you receive photos from iPhones and other phones: keep the originals, since converting to JPEG loses quality and metadata (depth, HDR gain maps).
• Use for storing photos in an Apple-centric workflow: macOS, iOS and iCloud Photos handle it everywhere.
• Avoid on the web: only Safari displays HEIC. Use JPEG, WebP or AVIF instead.
• Avoid for sharing with Windows users or uploading to sites that may not accept it; convert to JPEG first.
• Avoid in software you distribute if you can’t handle HEVC patent licensing: AVIF and JPEG XL give similar or better compression royalty-free.

Opening HEIC on Windows#

Windows 10 and 11 decode HEIC through two Microsoft Store packages:

1. HEIF Image Extensions (free, often preinstalled): the HEIF container.
2. HEVC Video Extensions (paid, about $1; some PCs come with a free OEM version): the HEVC decoder.

With both installed, File Explorer shows thumbnails and Photos, Paint and other apps that use the Windows Imaging Component (WIC) open .heic. Without the HEVC extension, Photos asks you to install it. Programs that include their own decoder (SumatraPDF, GIMP, XnView MP, ImageMagick) don’t need these extensions.

To avoid the problem on the iPhone side: Settings › Camera › Formats › Most Compatible takes JPEG photos, and Settings › Photos › Transfer to Mac or PC › Automatic converts to JPEG when copying over USB.

Patents and licensing#

HEVC is covered by patents held by many companies, licensed through the Access Advance and Via LA pools and by individual holders. Products that ship an HEVC decoder or encoder may owe royalties, depending on the country and the product. This is why Chrome, Firefox and Edge don’t display HEIC, why Windows sells the HEVC extension separately, and why many open-source projects ship HEIC support only as an optional plugin.

The open-source libraries (libheif, libde265, x265) are available under LGPL/GPL, but their copyright license doesn’t grant patent rights. The HEIF container itself, and AVIF files in it, are not affected by HEVC patents.

File structure#

A HEIF file is a sequence of boxes, the same structure as MP4. Each box starts with a 4-byte big-endian size and a 4-byte type; a size of 1 means a 64-bit size follows. “Full boxes” add a 1-byte version and 3 bytes of flags.

Unlike a video, a still image file is described by items: each image, thumbnail, Exif block or tile is an item with a numeric ID. The meta box lists the items and their properties and says where their data is; the data is in mdat.

00 00 00 18  66 74 79 70        box size 24, "ftyp"
68 65 69 63  00 00 00 00        major brand "heic", minor version 0
6D 69 66 31  68 65 69 63        compatible brands "mif1", "heic"
xx xx xx xx  6D 65 74 61        "meta": item descriptions (hdlr, pitm, iinf, iloc, iref, iprp)
xx xx xx xx  6D 64 61 74        "mdat": HEVC-coded tiles, thumbnail, Exif

Top-level boxes#

Brands#

Boxes inside meta#

Common item types in infe:

Common item references in iref:

Common properties in ipco:

Grid images#

HEVC encoders and hardware decoders work best on limited sizes, so phones store a photo as tiles. An iPhone photo of 4032 x 3024 is typically 48 HEVC images of 512 x 512 (8 columns x 6 rows), each an hvc1 item, plus a grid item that references them with dimg. The grid item is the primary item. Its data (often in idat) is short:

The tiles share one hvcC property. A decoder decodes each tile, places them left to right, top to bottom, crops to the output size and then applies clap, irot and imir. Orientation in HEIF comes from irot/imir; the Exif orientation tag should be ignored when displaying.

Other content in phone photos#

• a small HEVC thumbnail (thmb reference)
• a depth map for portrait mode and an HDR gain map (auxl references), which apps without support simply ignore
• Exif with camera data and GPS location, XMP
• Live Photos store the video in a separate .mov file

Converting HEIC#

heif-dec photo.heic photo.jpg           # libheif tool (called heif-convert in older versions)
heif-enc photo.png -q 50 -o photo.heic  # encode with x265
magick photo.heic -quality 90 photo.jpg # ImageMagick built with libheif
sips -s format jpeg photo.heic --out photo.jpg   # macOS built-in

Converting to JPEG keeps the main image and usually the Exif data, and drops depth maps, gain maps and other auxiliary images.

Specifications and documentation#

• ISO/IEC 23008-12: Image File Format (HEIF), paid
• ITU-T H.265: HEVC, free download from ITU
• ISO base media file format (ISO/IEC 14496-12): the box structure HEIF builds on
• HEIF technical information from Nokia: readable overview of items, properties and grids
• MPEG file format reference software
• libheif: the most used open-source implementation; its source is a good practical reference
• HEIF on Wikipedia
• Browser support on caniuse

Software that opens HEIC files#

Libraries#

Open-source libraries that read and write HEIC. See all HEIC libraries for a comparison.

Related formats#

• AVIF: the same HEIF container with AV1 instead of HEVC, royalty-free, supported by all browsers
• JPEG: what HEIC photos are usually converted to for sharing
• JPEG XL: royalty-free alternative with lossless JPEG recompression
• WebP: web image format, smaller than JPEG, less efficient than HEIC
• JPEG 2000: JP2 files use the same box layout (4-byte size, 4-byte type); HEIF can also carry JPEG 2000 images