Hooks let you run commands at specific points in Claude Code's lifecycle. The key difference between hooks and everything else covered in this course is that hooks are deterministic — they always run.
You can tell Claude in your CLAUDE.md to run Prettier after every file edit. Most of the time it will. But sometimes it won't. A hook makes it happen every single time, no exceptions.
Common use cases include:
Hooks are configured in your settings.json. You pick an event, optionally set a matcher for which tools it applies to, and provide a command to run. Some of the most common events are:
These are just a few of the events you can hook into — Claude Code supports many more. See the hooks reference for the full list.
You configure them through the /hooks command inside Claude Code, or by editing settings.json directly.
The most common hook: auto-formatting after edits. Set a PostToolUse hook with a matcher of "Edit|MultiEdit|Write" so it fires whenever Claude modifies a file. The command checks the file extension and runs the appropriate formatter — Prettier for TypeScript, gofmt for Go, whatever your project uses.
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PreToolUse hooks can block tool calls before they execute. Your hook receives the tool name and input as JSON on stdin. The exit code determines the behavior:
This is how you enforce hard rules. Block writes to a production config directory. Block bash commands that contain rm -rf. Block commits to main. Whatever your team needs to be guaranteed, not suggested.
Hooks configured in .claude/settings.json are project-level and can be checked into your repo. This means your entire team gets the same hooks automatically. Use the CLAUDE_PROJECT_DIR environment variable in your commands to reference scripts stored in your project, so they work regardless of Claude's current working directory.
Hooks give you deterministic control over Claude Code's behavior. Use PostToolUse for auto-formatting and logging. Use PreToolUse to block dangerous operations. Configure them with /hooks or in settings.json. And check them into your repo so your team gets them too.
If something needs to happen every time without fail, don't put it in a prompt. Put it in a hook.