Image MIME Reference
HEIF-Sequence
High Efficiency Image File Format Sequence
image/heif-sequence
VS
X Bitmap (Legacy MIME Alias)
image/x-xbm
XBM
A complete technical comparison of High Efficiency Image File Format Sequence and X Bitmap (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HEIF-Sequence | XBM |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| 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 Sequence
image/heif-sequence
Extension
.heifs.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 73 66 31
X Bitmap (Legacy MIME Alias)
image/x-xbm
Extension
.xbm
Container
C Source Code Header (.h)
Compression
Uncompressed (Source Code)
Algorithm
None
Color Depth
1-bit (Monochrome)
Developed by
MIT / X Consortium (X Window System)
Released
1988
Magic Bytes
23 64 65 66 69 6e 65 (ASCII '#define')
Browser Support Comparison
| Browser | HEIF-Sequence | XBM |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
HEIF-Sequence
HEIF-Sequence Strengths
- Codec-agnostic container allows for extreme flexibility when storing multi-frame photographic data
- Maintains the space-saving benefits of ISOBMFF shared frame data blocks
- Excellent for archiving computational photography workloads like exposure brackets or focal stacks
Limitations
- Codec ambiguity means a decoder might be able to parse the container but fail to decode the underlying pixels
- Zero native web browser support
- Complex container structure requires specialized parsing libraries to extract individual frames
XBM
XBM Strengths
- Can be compiled directly into C or C++ source code without needing an external file loader or binary asset manager
- Human-readable structure allows developers to inspect, edit, or hand-craft tiny icons directly within a text editor
- Extremely predictable and lightweight for 1-bit hardware displays and embedded systems
Limitations
- Strictly limited to 1-bit monochrome (black and white) graphics with no gray or color support
- Text-based C syntax creates massive file bloat compared to binary 1-bit formats like PBM
- Completely deprecated in modern web browsers and desktop GUI frameworks
When to choose which format
HEIF-Sequence
Use HEIF-Sequence when…
- Burst Photography
- Focal Stacking
- Exposure Bracketing
- Time-Lapse Data
XBM
Use XBM when…
- X Window System (X11) Cursors and Icons
- Embedded C/C++ Firmware UI Assets
- Early 1990s Unix Web Graphics