Package Manager Hooks

A reference documenting lifecycle hooks across package manager ecosystems, categorizing them into two types: package-defined hooks (scripts embedded by package authors that execute during installation, building, or publishing) and system/plugin hooks (extension points for users and tools to modify package manager behavior globally).

Covers hooks across npm, Yarn, pnpm, Cargo, pip, Composer, RubyGems, Maven, Gradle, and many others. For each ecosystem, it documents when hooks execute, their implementation mechanisms, and security implications.

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.