Claude Mods are JavaScript or TypeScript functions that run inside the Claude Code process and respond to events. They can react to a session, a turn, a tool call, or an interface event. A Mod is packaged as part of a Claude Code plugin; a plugin can include other components too.
A Mod is not the same thing as a Skill, an MCP server, or a classic settings hook. Skills provide reusable instructions, MCP connects external tools and data, and classic hooks are configured separately. See the official Mods overview, plugins, Skills, MCP, and hooks documentation for the current distinctions.
What can they do?
Some Mods draw interface elements, while others react to events without drawing anything. For example, token-ledger shows token and cost information, cc-pr-tracker follows pull request status, and launch-codes adds a confirmation step for certain Bash commands. These are author descriptions and source reviews, not our own runtime test results.
Before installing
Mods execute with your user permissions and are not sandboxed. Check the repository, install instructions, dependencies, and reported compatibility for each Mod before using it in a sensitive environment. Our methodology distinguishes source review from local validation and functional tests. Continue with the installation guide or troubleshooting guide.