PAM file format: what it is and how to use it

PAM is the Portable Arbitrary Map, the Netpbm family's general member, storing any channel layout and depth in a simple headered raw format. Learn when to use it and what to choose instead.

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What is a PAM file?

A .pam file is an image in Portable Arbitrary Map, the generalization of the Netpbm formats: a tiny header declaring width, height, depth (channels), maxval and tuple type, then raw pixel data. Where PBM is 1-bit, PGM grayscale and PPM RGB, PAM covers all of them plus alpha and arbitrary channel layouts, the family's Swiss-army knife for pipes.

When should you use PAM?

  • Netpbm pipelines: the format that carries RGBA and multi-channel data through their tools.
  • Simple raw interchange: trivially parsed by a few lines of code.
  • Scripted image processing: when structure matters more than compression.

When is another format a better fit?

For anything stored or shared, PNG is the obvious answer: same pixels, real compression, universal support. For the simpler family members PBM/PGM/PPM cover the classic cases. PAM is a tool of pipelines, not a delivery format.

The short version: PAM is the Netpbm family's general member: handy in a shell pipeline, but out of place anywhere else.

How to open a PAM file

On Windows

Double-click the file, or open it with GIMP.

In your browser

Open PAM files right in a browser tab or with the dexrr viewer. No install, no upload.

Also opens in

  • Netpbm tools
  • ImageMagick
  • GIMP

View or convert PAM files

A quick preview or a new format. No install, no upload.

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PAM technical details

Full name
Portable Arbitrary Map
Extensions
.pam
MIME type
image/x-portable-arbitrarymap
Magic bytes
50 37 (P7)
Compression
None (uncompressed)
Developer
Netpbm project
Specification
netpbm.sourceforge.net

PAM questions, answered

How do I open a .pam file?

Netpbm tools, ImageMagick, GIMP and FFmpeg read it; OS viewers rarely do. dexrr displays and converts pam files directly in your browser.

Can I convert PAM files online?

Yes, dexrr converts pam locally in your browser: PAM to PNG for normal use or PAM to JPG for opaque images.

Is PAM better than PPM?

It is the superset, since PPM is RGB-only PAM essentially. For plain RGB both work; for alpha or unusual channels you need PAM.

Why does my .pam file not open in my viewer?

It is a specialist pipe format, and most general viewers never implemented it. Convert to PNG and every tool reads it.

Is the PAM format outdated?

Stable and niche. It lives inside Netpbm workflows and nowhere else needs it.