Image MIME Reference
RealPix
RealNetworks RealPix
image/vnd.rn-realpix
VS
Scalable Vector Graphics
image/svg+xml
SVG
A complete technical comparison of RealNetworks RealPix 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 | RealPix | SVG |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | Yes | Yes |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
RealNetworks RealPix
image/vnd.rn-realpix
Extension
.rp
Container
IMFL (XML Markup)
Compression
Uncompressed (Plain Text Markup)
Algorithm
None (Plain Text)
Color Depth
Dependent on referenced images
Developed by
RealNetworks
Released
1998
Magic Bytes
3C 69 6D 66 6C
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 | RealPix | SVG |
|---|---|---|
Chrome
|
✕ |
✓ All
|
Firefox
|
✕ |
✓ All
|
Safari
|
✕ |
✓ All
|
Edge
|
✕ |
✓ All
|
IE (Legacy)
|
✕ |
✓
|
RealPix
RealPix Strengths
- Allowed for 'Ken Burns'-style animated slideshows at a fraction of the bandwidth required for actual video, crucial for 1990s dial-up connections
- Plain text XML architecture made it easy for developers and hobbyists to hand-code complex multimedia presentations
- Perfectly synchronized with RealAudio streams using SMIL-like timing parameters
Limitations
- Completely obsolete and heavily reliant on the proprietary, defunct RealPlayer browser plugin
- Not a true image format, causing confusion when handled by standard image processing libraries which expect binary pixel data
- Lacks modern CSS or HTML5 canvas equivalents without completely rewriting the presentation logic
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
RealPix
Use RealPix when…
- Historical Dial-up Streaming Presentations
- RealPlayer Slideshows
- Bandwidth-efficient 'Video' Alternatives (late 1990s)
SVG
Use SVG when…
- Web Logos & UI Icons
- Responsive Web Design Elements
- Interactive Data Visualizations (D3.js)
- CSS and SMIL Web Animations