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Image MIME Reference
GIF

Graphics Interchange Format

image/gif
VS

Portable Graymap

image/x-portable-graymap
PGM

A complete technical comparison of Graphics Interchange Format and Portable Graymap — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

GIF wins on browser support

Feature Support

Feature GIF PGM
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No ✕ No
ICC Color Profile Yes ✕ No
Graphics Interchange Format
image/gif
Extension
.gif
Container GIF
Compression Lossless (LZW)
Algorithm
LZW (Lempel-Ziv-Welch)
Color Depth 1-bit, 4-bit, 8-bit (Indexed)
Developed by CompuServe
Released 1987
Magic Bytes
47 49 46 38 39 61
Full GIF reference →
Portable Graymap
image/x-portable-graymap
Extension
.pgm
Container Netpbm
Compression Uncompressed
Algorithm
None
Color Depth 8-bit (Grayscale), 16-bit (Grayscale)
Developed by Jef Poskanzer (Netpbm Project)
Released 1988
Magic Bytes
50 32 (ASCII) or 50 35 (Binary)
Full PGM reference →

Browser Support Comparison

Browser GIF PGM
Chrome Chrome
✓ All
 ✕
Firefox Firefox
✓ All
 ✕
Safari Safari
✓ All
 ✕
Edge Edge
✓ All
 ✕
IE IE (Legacy)
✓
 ✕
GIF

GIF Strengths

  • Universal support across all web browsers, operating systems, and messaging apps
  • Supports basic frame-by-frame animation out of the box
  • Lossless compression is highly effective for simple, flat-color graphics like logos or pixel art
Limitations
  • Limited to 256 colors per frame, resulting in poor quality for complex gradients and photographs
  • Animations produce massive file sizes compared to modern formats like MP4, WebP, or AVIF
  • 1-bit transparency limits edge blending on non-uniform backgrounds
PGM

PGM Strengths

  • Extremely simple format allows custom parsers to be written from scratch in minimal time
  • Supports 16-bit precision, making it highly valuable for scientific, medical, and height-map data where 8-bit precision is insufficient
  • ASCII encoding ('P2') allows manual editing and visual inspection of pixel values directly within a text editor
Limitations
  • Strictly limited to grayscale; cannot display color
  • Lack of compression results in massive file sizes, making it entirely impractical for web delivery or consumer storage
  • Does not support alpha transparency or modern metadata structures

When to choose which format

GIF
Use GIF when…
  • Web Animations
  • Memes
  • Simple Graphics
  • Logos with flat colors
PGM
Use PGM when…
  • Computer Vision and Machine Learning Pre-processing
  • Scientific and Medical Image Processing
  • Unix/Linux Command-Line Image Pipelines

More comparisons

GIF vs ACES → PGM vs ACES → GIF vs APNG → PGM vs APNG → GIF vs AVCI → PGM vs AVCI → GIF vs AVCS → PGM vs AVCS → GIF vs AVIF → PGM vs AVIF → All comparisons →
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