1. Check your version

Mods need Claude Code 2.1.287 or later, the release that turned them on by default. In your terminal:

claude --version

If it's older, update with claude update.

2a. Install from a marketplace

Most mods live in a repo that is also a plugin marketplace. Add the marketplace once, then install the mod. Run both inside Claude Code:

/plugin marketplace add <owner>/<repo>
/plugin install <mod>@<marketplace>

Each mod page on Modshelf shows the exact two lines, with a copy button.

2b. Or load it straight from its folder

For a mod that isn't in a marketplace, or one you want to read first, clone it and start Claude Code with --plugin-dir. It loads for that session only, and reloads when the files change.

git clone https://github.com/<owner>/<repo> ~/mods/<repo>
claude --plugin-dir ~/mods/<repo>

3. Check it loaded

Run /plugin and press Tab until the Installed tab is selected. The mod is listed there, and you can turn it off from the same screen.

If a mod does nothing

Run claude plugin validate on its folder. It catches a bad manifest or a misspelled event without starting a session.
Start once with claude --debug and look for a line that starts with hooks module and the mod's name. It says why the mod didn't load.
Opened a folder for the first time? Accept the trust prompt. Mods don't load in a folder you haven't trusted.
--safe-mode, --bare and the disableAllHooks setting all stop mods.

Anthropic's troubleshooting guide lists every message and what it means.

Before you install anything

A mod runs with your permissions. Each page here says what the mod can reach, from drawing on screen to using the network. Here's how we decide.