Image MIME Reference
PPM
Portable Pixmap
image/x-portable-pixmap
VS
WebP Image
image/webp
WebP
A complete technical comparison of Portable Pixmap and WebP Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
WebP wins on browser support
Feature Support
| Feature | PPM | WebP |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
Portable Pixmap
image/x-portable-pixmap
Extension
.ppm
Container
Netpbm
Compression
Uncompressed
Algorithm
None
Color Depth
24-bit (RGB), 48-bit (RGB High Color)
Developed by
Jef Poskanzer (Netpbm Project)
Released
1988
Magic Bytes
50 33 (ASCII) or 50 36 (Binary)
WebP Image
image/webp
Extension
.webp
Container
RIFF
Compression
Lossy / Lossless
Algorithm
VP8VP8L
Color Depth
8-bit
Developed by
Google
Released
2010
Magic Bytes
52 49 46 46 XX XX XX XX 57 45 42 50
Browser Support Comparison
| Browser | PPM | WebP |
|---|---|---|
Chrome
|
✕ |
✓ 32+
|
Firefox
|
✕ |
✓ 65+
|
Safari
|
✕ |
✓ 14+
|
Edge
|
✕ |
✓ 18+
|
IE (Legacy)
|
✕ | ✕ |
PPM
PPM Strengths
- Absolute structural simplicity allows parsers and renderers (such as custom raytracers) to write directly to the format with virtually no overhead or external libraries
- Supports 16-bit per channel (48-bit total) precision, preserving deep color accuracy before converting to final delivery formats
- ASCII encoding ('P3') allows manual editing and visual inspection of RGB values directly within a text editor
Limitations
- Zero compression results in astronomical file sizes, making it entirely impractical for web delivery or consumer storage
- Does not natively support an alpha channel for transparency (this is handled by the newer PAM extension format within the Netpbm suite)
- Lacks support for modern metadata standards like EXIF, XMP, or embedded ICC color profiles
WebP
WebP Strengths
- Superior lossy compression — 25–35% smaller than JPEG at equivalent quality
- Supports both animation and full alpha transparency
- Lossless mode available with smaller file sizes than PNG
Limitations
- Slower encoding than JPEG, especially for lossless
- Not supported in Internet Explorer or very old browsers
When to choose which format
PPM
Use PPM when…
- Intermediary Format for Image Format Conversion
- Academic Computer Graphics and Raytracing Output
- Unix/Linux Command-Line Image Pipelines
WebP
Use WebP when…
- Websites
- Ecommerce
- Mobile Apps
- CMS Images