Package Manager Archives

Documentation of archive formats used by package managers, covering both language-specific ecosystems (gems, wheels, npm tarballs, crates) and system-level formats (deb, rpm, apk).

Each entry documents internal archive structure, compression methods, metadata file locations, implementation quirks, and edge cases that commonly cause problems. Ruby gems use nested gzip compression within tar archives; Python wheels are actually ZIP files with specific metadata requirements; npm packages employ pax extended headers for long filenames.

Background

This work was originally posted on blog.ecosyste.ms on November 17, 2025.

Package managers are the quiet workhorses of computing. They make installing software on a machine trivial, but they have their differences, and as recent events have shown, those differences can lead to vulnerabilities and provide opportunities for attackers to disrupt public and private services alike.

ecosyste.ms is in something of a unique position: having aggregated and normalized package data from over 70 sources we know something about how package managers work, and how they differ from one another.

Working alongside the CHAOSS Package Metadata Working Group and Alpha-Omega we've documented the similarities and differences across package registries and clients, publishing multiple repositories of information about how package managers work, including the data in this post. In doing so we hope to identify common problems and work toward better practices.

This repository is released under CC0 1.0 Universal and accepts contributions if you have corrections or additions.