Image MIME Reference
HEIF
High Efficiency Image File Format
image/heif
VS
Image Exchange Format
image/ief
IEF
A complete technical comparison of High Efficiency Image File Format and Image Exchange Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HEIF | IEF |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | Yes | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
High Efficiency Image File Format
image/heif
Extension
.heif.hif
Container
HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression
Lossy / Lossless
Algorithm
Codec Agnostic (HEVC, AVC, JPEG, AV1)
Color Depth
8-bit, 10-bit, 12-bit, 16-bit
Developed by
Moving Picture Experts Group (MPEG)
Released
2015
Magic Bytes
XX XX XX XX 66 74 79 70 6D 69 66 31
Image Exchange Format
image/ief
Extension
.ief
Container
TIFF Class B (TIFF-B)
Compression
Lossless (MH, MR, MMR) / Uncompressed
Algorithm
MHMRMMRUncompressed
Color Depth
1-bit (Monochrome)
Developed by
IETF Network Fax Working Group
Released
1992
Magic Bytes
49 49 2A 00 (Little-endian) / 4D 4D 00 2A (Big-endian)
Browser Support Comparison
| Browser | HEIF | IEF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
HEIF
HEIF Strengths
- Highly flexible container that can store image bursts, animations, focal stacks, and stereo 3D images in one file
- Natively supports depth maps and alpha channels, making it perfect for computational photography
- When paired with modern codecs like HEVC or AV1, it provides massive storage savings over legacy formats like JPEG
Limitations
- Codec agnosticism makes broad software decoding difficult, as the container might hold proprietary or unsupported codecs
- Zero cross-platform web browser support, requiring conversion for online publishing
- Often confused with the more specific 'image/heic' and 'image/avif' MIME types
IEF
IEF Strengths
- Provided a standard method for exchanging bi-level fax images during the early days of the Internet
- Supported multi-page documents
- Leveraged the highly resilient and well-documented TIFF container
Limitations
- Completely obsolete and unsupported in modern computing environments
- Strictly limited to 1-bit monochrome data, lacking color or grayscale capabilities
- Magic bytes overlap completely with standard TIFF, making specific filetype detection difficult without parsing internal tags
When to choose which format
HEIF
Use HEIF when…
- Digital Photography
- Camera Capture
- Image Archiving
- Multi-image composites
IEF
Use IEF when…
- Legacy Fax Transmissions
- Early Internet Gateways
- Archival