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Image MIME Reference
CMU-Raster

CMU Window Manager Raster

image/x-cmu-raster
VS

JPEG Image

image/jpeg
JPEG

A complete technical comparison of CMU Window Manager Raster and JPEG Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

JPEG wins on browser support

Feature Support

Feature CMU-Raster JPEG
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No Yes
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
CMU Window Manager Raster
image/x-cmu-raster
Extension
.ras
Container CMU Window Manager Bitmap
Compression Uncompressed
Algorithm
None
Color Depth 1-bit (Monochrome), 8-bit (Indexed/Grayscale)
Developed by Carnegie Mellon University (CMU)
Released 1980s
Magic Bytes
F1 00 40 BB
Full CMU-Raster reference →
JPEG Image
image/jpeg
Extension
.jpg.jpeg.jpe.jfif
Container JFIF / Exif
Compression Lossy
Algorithm
DCT (Discrete Cosine Transform)
Color Depth 8-bit
Developed by Joint Photographic Experts Group
Released 1992
Magic Bytes
FF D8 FF
Full JPEG reference →

Browser Support Comparison

Browser CMU-Raster JPEG
Chrome Chrome
✕
✓ All
Firefox Firefox
✕
✓ All
Safari Safari
✕
✓ All
Edge Edge
✕
✓ All
IE IE (Legacy)
✕
✓
CMU-Raster

CMU-Raster Strengths

  • Incredibly simple, uncompressed binary structure that was easy for early, memory-constrained UNIX workstations to parse and render
Limitations
  • Completely obsolete and unsupported outside of niche historical command-line tools like Netpbm
  • The shared '.ras' file extension causes frequent file misidentification and system conflicts
  • Lacks all modern imaging features, including metadata, compression, and alpha channel transparency
JPEG

JPEG Strengths

  • Universal support — every browser, OS, and application handles JPEG
  • Excellent compression for complex photographs with natural color gradients
  • Rich metadata support: EXIF (GPS, camera settings), ICC color profiles
Limitations
  • No transparency — cannot have a transparent background
  • Lossy compression introduces visible artifacts on sharp edges and text
  • No animation support

When to choose which format

CMU-Raster
Use CMU-Raster when…
  • Historical UNIX / Andrew Project Archival
  • Legacy Academic Computing Research
JPEG
Use JPEG when…
  • Photography
  • Websites
  • Social Media
  • Print

More comparisons

CMU-Raster vs ACES → JPEG vs ACES → CMU-Raster vs APNG → JPEG vs APNG → CMU-Raster vs AVCI → JPEG vs AVCI → CMU-Raster vs AVCS → JPEG vs AVCS → CMU-Raster vs AVIF → JPEG vs AVIF → All comparisons →
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