Image MIME Reference
G3-Fax
Group 3 Fax Image
image/g3fax
VS
Scalable Vector Graphics
image/svg+xml
SVG
A complete technical comparison of Group 3 Fax Image and Scalable Vector Graphics — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
SVG wins on browser support
Feature Support
| Feature | G3-Fax | SVG |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
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)
Scalable Vector Graphics
image/svg+xml
Extension
.svg.svgz
Container
XML Document
Compression
Uncompressed (Plain Text XML) / Lossless (GZIP via .svgz)
Algorithm
None (for .svg)GZIP (for .svgz)
Color Depth
Vector (Independent of bit-depth), CSS Colors (HEX, RGB, HSL, Display-P3)
Developed by
World Wide Web Consortium (W3C)
Released
2001
Magic Bytes
3C 73 76 67 (for <svg) / 3C 3F 78 6D 6C (for <?xml)
Browser Support Comparison
| Browser | G3-Fax | SVG |
|---|---|---|
Chrome
|
✕ |
✓ All
|
Firefox
|
✕ |
✓ All
|
Safari
|
✕ |
✓ All
|
Edge
|
✕ |
✓ All
|
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
SVG
SVG Strengths
- Provides infinite resolution scalability, looking perfectly crisp on high-DPI (Retina) displays without increasing file size
- Extremely lightweight compared to raster formats for flat graphics, logos, and UI elements
- Can be manipulated dynamically via the browser's CSS and JavaScript engines (DOM integration)
Limitations
- Unsuitable for complex photographic images or photorealistic textures
- Poses critical security vulnerabilities (XSS and XML External Entity attacks) if user-uploaded SVGs are not heavily sanitized
- Rendering performance degrades significantly if the SVG contains tens of thousands of complex nodes or deeply nested paths
When to choose which format
G3-Fax
Use G3-Fax when…
- Telefacsimile (Fax) Transmission
- Internet Fax (T.37)
- Document Archiving
- Telephony Systems
SVG
Use SVG when…
- Web Logos & UI Icons
- Responsive Web Design Elements
- Interactive Data Visualizations (D3.js)
- CSS and SMIL Web Animations