File Format Encyclopedia

Your resource for file format specifications.

Wotsup.org is a community-driven archive providing hundreds of file format specifications, hardware notes, and implementation guides. Browse and contribute to help keep legacy data accessible.

Start contributing How to use

• 723+ file formats
• 21+ categories
• Community maintained

Quick links

• How to use
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What's inside

A comprehensive format reference library.

Formats documented

723

Detailed specifications, diagrams, and implementation tips.

Categories covered

21

From graphics and audio to printers, CAD, and communications.

Specs archived

1042+

Reference files, whitepapers, and utility documentation.

Explore the collection

Browse by format and category to find specs and decoding notes. For keyword searches, try a search engine with site:wotsup.org.

Explore the information architecture →

Engineering ready

Entries focus on structures, fields, and practical tips for building parsers.

Developer guidance →

Community powered

Submit corrections or new specs via GitHub. Every contribution is reviewed.

Contributing guide →

Get involved

Help expand the documentation.

Contribute format specifications, add implementation notes, or improve existing documentation. All contributions are welcome via GitHub.

• Submit specs via GitHub
• Add decoding tips
• Improve metadata + tagging

New to the archive?

Start with the quick guides.

Learn how to navigate the archive and find the format information you need.

How to use Wotsup.org Frequently asked questions Contact + support

Recent additions

Latest updates to the catalog.

1. Jul 13, 2026

   .rss updated Syndication file format

   .css updated Cascading Style Sheets 1

2. Jul 12, 2026

   .xml updated Extensible Markup Language (XML) 1.0

   .html updated HTML 2.0 (RFC 1866 approved by IETF)

   .csv updated Comma Separated Value Files

   .rtf updated Rich Text File Format v1.5 (MS Word)

3. Jul 10, 2026

   .arj updated ARJ File Format

   .zlib updated ZLIB Compressed Data Format Specification version 3.3

4. Jul 8, 2026

   .bz2 updated Bzip 2 archives

   .gzip updated GZIP file format specification

   .cab updated MS CAB file format with source

   .rar updated RAR 2.00 Format

   .tar updated TAR Archive File Format

   .7z updated 7Zip LZMA Compression SDK

5. Jul 7, 2026

   .mif updated MapInfo Interchange Format (MIF/MID)

Ready to contribute?

Every contribution helps keep file format knowledge accessible. Fork the repo, add your notes, and submit a pull request.

View the repository Contribution guide

Built on the foundation of Wotsit.org, originally created by Paul Oliver and contributors worldwide. Thanks to their pioneering work in documenting file formats. Read more about Wotsup.org →