Git Blame: Track Who Changed Every Line

What Does git blame Do?

git blame annotates each line of a file with the commit hash, author, and date of the last change to that line. It is an investigative tool for understanding the history behind specific code.

Basic Usage

# Blame an entire file
git blame src/app.tsx

# Blame specific line range
git blame -L 10,20 src/app.tsx

# Blame starting from a specific function (regex)
git blame -L '/function App/,/^}/' src/app.tsx

Output Format

a1b2c3d4 (Jane Doe 2025-03-15 14:22:01 +0000 10) function App() {
f4e5d6a7 (John Smith 2025-04-02 09:11:33 +0000 11)   const [count, setCount] = useState(0);
a1b2c3d4 (Jane Doe 2025-03-15 14:22:01 +0000 12)   return <div>{count}</div>;

Ignoring Whitespace and Formatting Changes

Large reformatting commits can obscure meaningful blame data. Use -w to ignore whitespace:

git blame -w src/app.tsx

For projects that have had major formatting commits (e.g., running Prettier for the first time), create a .git-blame-ignore-revs file:

# .git-blame-ignore-revs
# Prettier reformatting
a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0

git config blame.ignoreRevsFile .git-blame-ignore-revs

Going Deeper

To see the full commit that changed a line:

git blame src/app.tsx
# Note the hash, then:
git show a1b2c3d4

Tips

Git blame is not about assigning fault — it is about understanding context. When you find a confusing line of code, blame reveals the commit message and PR that introduced it, giving you the "why" behind the code. Combine it with git log -p for a complete picture.