Free webp to jpg
EN
Image MIME Reference
PGM

Portable Graymap

image/x-portable-graymap
VS

WebP Image

image/webp
WebP

A complete technical comparison of Portable Graymap 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 PGM 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 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 →
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
Full WebP reference →

Browser Support Comparison

Browser PGM WebP
Chrome Chrome
✕
✓ 32+
Firefox Firefox
✕
✓ 65+
Safari Safari
✕
✓ 14+
Edge Edge
✕
✓ 18+
IE IE (Legacy)
✕ ✕
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
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

PGM
Use PGM when…
  • Computer Vision and Machine Learning Pre-processing
  • Scientific and Medical Image Processing
  • Unix/Linux Command-Line Image Pipelines
WebP
Use WebP when…
  • Websites
  • Ecommerce
  • Mobile Apps
  • CMS Images

More comparisons

PGM vs ACES → WebP vs ACES → PGM vs APNG → WebP vs APNG → PGM vs AVCI → WebP vs AVCI → PGM vs AVCS → WebP vs AVCS → PGM vs AVIF → WebP vs AVIF → All comparisons →
Share this comparison