High Efficiency Image Container
Convert HEIC photos from your iPhone to JPG, PNG, or WebP directly in your browser — no upload, no server, no app install. FileDex decodes HEIC locally using WebAssembly and re-encodes to your target format in seconds, keeping your photos private.
HEIC codec not compiled into FFmpeg WASM build
Common questions
Why can't I open HEIC photos from my iPhone on Windows?
Windows does not include an HEVC decoder by default due to patent licensing costs. Install the free 'HEIF Image Extensions' from the Microsoft Store, then install the 'HEVC Video Extensions' ($0.99) or the free 'HEVC Video Extensions from Device Manufacturer' if available for your hardware.
How do I stop my iPhone from taking HEIC photos?
Go to Settings > Camera > Formats and select 'Most Compatible' instead of 'High Efficiency.' This switches the camera to JPEG output. Alternatively, keep High Efficiency and enable Settings > Photos > Transfer to Mac or PC > Automatic, which converts to JPEG during transfers.
Does converting HEIC to JPG lose quality?
Some quality loss occurs because JPEG uses DCT compression while HEIC uses HEVC — they are fundamentally different algorithms. At JPEG quality 90+, the difference is minimal for typical smartphone photos. The bigger visual change comes from tone-mapping 10-bit HDR content down to 8-bit sRGB.
Can I batch convert hundreds of HEIC files at once?
Yes. Use ImageMagick: magick mogrify -format jpg -quality 90 *.heic to convert all HEIC files in a directory. FileDex also supports multiple files — drop them all into the converter zone. For very large batches (1000+), the CLI approach is faster.
Why are HEIC files smaller than JPEG at better quality?
HEIC uses the HEVC (H.265) codec, which employs variable-size coding tree units up to 64x64 pixels, advanced intra prediction modes, and context-adaptive binary arithmetic coding (CABAC). JPEG's 8x8 DCT blocks and Huffman coding are less efficient. HEVC was designed 20 years after JPEG with decades of compression research applied.
What makes .HEIC special
What is a HEIC file?
HEIC (High Efficiency Image Container) is a file format based on the HEIF (High Efficiency Image File Format) standard. It uses the HEVC (H.265) codec for compression, achieving roughly 50% smaller file sizes than JPEG at the same visual quality.
Continue reading — full technical deep dive
How to open HEIC files
- Apple devices (iPhone, iPad, Mac) — Native support since iOS 11 and macOS High Sierra
- Windows 10/11 — Install "HEIF Image Extensions" from Microsoft Store
- GIMP (Windows, macOS, Linux) — Free, with plugin
- Adobe Photoshop (Windows, macOS) — Native support since CC 2020
Technical specifications
| Property | Value |
|---|---|
| Compression | HEVC (H.265) |
| Bit Depth | 8-bit, 10-bit, 12-bit |
| Color Spaces | sRGB, Display P3, Rec. 2020 |
| Alpha Channel | Supported |
| Animation | Supported (HEICS) |
| Multi-image | Supported (bursts, live photos) |
Why convert HEIC?
While HEIC offers superior compression, compatibility remains limited. Many web platforms, email clients, and older software don't support HEIC. Converting to JPEG or PNG ensures universal compatibility.
.HEIC compared to alternatives
| Formats | Criteria | Winner |
|---|---|---|
| .HEIC vs .JPG | Compression efficiency at equivalent quality HEIC HEVC intra-frame compression produces 40-50% smaller files than JPEG at matched visual quality. HEVC uses larger variable block sizes (up to 64x64) and more advanced prediction modes than JPEG's fixed 8x8 DCT. | HEIC wins |
| .HEIC vs .WEBP | Compression and feature set HEIC achieves approximately 20% better compression than WebP VP8 lossy. HEIC also supports 10-bit HDR, multi-image containers (Live Photos, bursts), and depth maps — features absent from WebP. | HEIC wins |
| .HEIC vs .AVIF | Compression efficiency and licensing AVIF AV1 matches or slightly exceeds HEVC compression efficiency while being completely royalty-free. HEIC/HEVC requires patent licensing through MPEG LA, limiting adoption in open-source projects. | AVIF wins |
| .HEIC vs .PNG | File size for photographic content HEIC is 20-50x smaller than PNG for photographs. PNG lossless compression cannot discard perceptual redundancy the way HEVC does. PNG is better suited for graphics with hard edges and text. | HEIC wins |
Technical reference
- MIME Type
image/heic- Magic Bytes
00 00 00 xx 66 74 79 70ISO base media ftyp box with heic/heix brand.- Developer
- Moving Picture Experts Group
- Year Introduced
- 2015
- Open Standard
- Yes — View specification
ISO base media ftyp box with heic/heix brand.
Binary Structure
HEIC uses the ISO Base Media File Format (ISOBMFF / ISO 14496-12) container, identical to MP4 and MOV. The file begins with an ftyp box declaring the brand (heic for single image, heics for sequence). Data is organized into boxes: moov contains metadata and item references, mdat holds compressed HEVC intra-frame bitstream data. Each image item is referenced via iloc (item location) and iprp (item properties) boxes. Multi-image files (Live Photos, bursts) store multiple items in the same container with iref (item reference) linking primary and auxiliary images.
| Offset | Length | Field | Example | Description |
|---|---|---|---|---|
0x00 | 4 bytes | Box size | 00 00 00 18 | Size of the ftyp box in bytes (big-endian uint32). Typically 24 bytes for HEIC. |
0x04 | 4 bytes | Box type | 66 74 79 70 | ASCII 'ftyp' — file type box, always first box in ISOBMFF files. |
0x08 | 4 bytes | Major brand | 68 65 69 63 | ASCII 'heic' for HEIC single image, 'heics' for image sequence, or 'mif1' for generic HEIF. |
0x0C | 4 bytes | Minor version | 00 00 00 00 | Version of the brand specification. Typically 0. |
0x10 | variable | Compatible brands | 6D 69 66 31 68 65 69 63 | List of compatible brands (mif1, heic, etc.) for reader compatibility detection. |
variable | variable | meta box | 6D 65 74 61 | Contains pitm (primary item), iloc (item locations), iprp (item properties), and iref (item references). |
variable | variable | mdat box | 6D 64 61 74 | Media data box containing HEVC-compressed image bitstream data. |
Attack Vectors
- HEVC decoder vulnerabilities — crafted HEIC files can trigger heap overflows in HEVC parsing libraries (libde265, x265)
- ISOBMFF box parsing exploits — deeply nested or oversized boxes can cause stack overflow or integer overflow in container parsers
- EXIF metadata privacy leak — HEIC files from iPhones embed precise GPS coordinates, device identifiers, and timestamps
- Multi-image container abuse — malicious auxiliary items hidden alongside primary image in the same HEIC container
Mitigation: FileDex decodes HEIC in the browser using heic2any WASM library within the browser sandbox. No server upload occurs. EXIF metadata is stripped during conversion to JPG/PNG/WebP.