Image MIME Reference
G3-Fax
Group 3 Fax Image
image/g3fax
VS
JPEG 2000 Compound Image File Format
image/jpm
JPM
A complete technical comparison of Group 3 Fax Image and JPEG 2000 Compound Image File Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | G3-Fax | JPM |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | Yes |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
Group 3 Fax Image
image/g3fax
Extension
.g3
Container
Raw Bitstream
Compression
Lossless (CCITT Group 3)
Algorithm
CCITT Group 3 (Modified Huffman / READ)
Color Depth
1-bit (Monochrome)
Developed by
CCITT (now ITU-T) / IETF
Released
1980
Magic Bytes
None (Raw Bitstream)
JPEG 2000 Compound Image File Format
image/jpm
Extension
.jpm.jpgm
Container
ISOBMFF / JPM (ISO/IEC 15444-6)
Compression
Lossy / Lossless / Mixed Raster Content (MRC)
Algorithm
JPEG 2000JBIG2JPEGMMR
Color Depth
1-bit (Text/Masks), 8-bit, 16-bit, 24-bit
Developed by
Joint Photographic Experts Group (JPEG)
Released
2003
Magic Bytes
00 00 00 0C 6A 50 20 20 0D 0A 87 0A ... 66 74 79 70 6A 70 6D 20
Browser Support Comparison
| Browser | G3-Fax | JPM |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
G3-Fax
G3-Fax Strengths
- Extremely efficient compression for 1-bit black-and-white text and line art
- Standardized via RFC 1494 for email and internet fax transmission
- Low bandwidth requirements
Limitations
- Raw format lacks metadata (such as image width and resolution), requiring out-of-band information to decode accurately
- Strictly limited to 1-bit monochrome imagery
- Zero native web browser support
JPM
JPM Strengths
- Highly optimized for scanned documents, drastically reducing file sizes without sacrificing the readability of text or the quality of embedded photos
- Supports multi-page documents within a single file
- Object-based architecture allows for complex layout representation and independent extraction of elements
Limitations
- Failed to achieve widespread adoption, largely being overshadowed by PDF/A and DjVu
- Zero native web browser compatibility
- Requires complex, specialized software to properly encode and decode the multi-layered MRC structure
When to choose which format
G3-Fax
Use G3-Fax when…
- Telefacsimile (Fax) Transmission
- Internet Fax (T.37)
- Document Archiving
- Telephony Systems
JPM
Use JPM when…
- Scanned Document Archiving
- Mixed Raster Content (MRC) Imaging
- Digital Libraries