Introduction

Git hooks are powerful tools that let you automate tasks during the Git workflow. One of the most commonly used hooks is the pre-commit hook. This script runs before a commit is finalized, making it ideal for tasks like linting code, running tests, or formatting files automatically.

In this post, you’ll learn what Git pre-commit hooks are, how to use them, and see examples with plain shell scripts and modern tools like Husky.

What is a Git Pre-Commit Hook?

A pre-commit hook is a script that runs right before a git commit is executed. If the script exits with a non-zero status, the commit will be aborted. This makes it a useful safeguard to prevent bad or broken code from being committed.

Git looks for hooks in the .git/hooks directory inside your repository.

How to Use Pre-Commit Hooks

1. Using Native Git Hooks

Git initializes example hooks when you create a repository. To enable the pre-commit hook:

1. Navigate to .git/hooks/
2. Rename pre-commit.sample to pre-commit
3. Make the file executable:

chmod +x .git/hooks/pre-commit

Example: Lint Code Before Commit

Here's a simple pre-commit script that runs ESLint before allowing the commit:

#!/bin/sh
 
echo "Running ESLint..."
npx eslint . || {
  echo "ESLint failed. Commit aborted."
  exit 1
}

If ESLint fails, the commit will not proceed.

2. Using Husky (Recommended for Teams)

Native Git hooks aren't shared with the repo. To version-control your hooks and ensure everyone runs them, use Husky.

Install Husky

npm install husky --save-dev
npx husky install

Add this to your package.json scripts:

"scripts": {
  "prepare": "husky install"
}

Add a Pre-Commit Hook

npx husky add .husky/pre-commit "npm run lint"

This creates a .husky/pre-commit file with:

#!/bin/sh
. "$(dirname "$0")/_/husky.sh"
 
npm run lint

Now every time you run git commit, Husky will trigger the hook and run your lint script.

Common Uses for Pre-Commit Hooks

• Linting code (eslint, stylelint)
• Running unit tests
• Formatting code with prettier
• Checking commit message format
• Preventing large files from being committed
• Type checking (tsc)

Tips

• Always make sure your pre-commit scripts are fast. If they take too long, developers will disable them.
• Keep hooks in version control using tools like Husky or lefthook.
• Avoid modifying committed files in pre-commit hooks (e.g., formatting) — instead, do that in a pre-push or prettier --write script and stage them manually.

Conclusion

Git pre-commit hooks are a great way to improve code quality and enforce consistency before code is committed. Whether you’re working solo or on a team, adding pre-commit hooks can help catch mistakes early and reduce tech debt.

By using tools like Husky, you can easily manage these hooks in your repo and make sure everyone on your team benefits from them.

Start small — add a linter or formatter hook, and build from there!

Happy committing! 🚀