Git Blame: Track Who Changed Every Line of Code

Git Blame: Line-by-Line Code Archaeology

git blame annotates each line of a file with the commit, author, and date of the last modification. It is essential for understanding code ownership and change history.

Basic Usage

# Blame entire file
git blame src/auth/login.ts

Output:

abc1234 (Jane Doe 2025-03-15) import { hashPassword } from './crypto';
def5678 (Bob Smith 2025-04-02) import { validateEmail } from './validate';
ghi9012 (Jane Doe 2025-03-15)
abc1234 (Jane Doe 2025-03-15) export async function login(email, password) {
jkl3456 (Carol Lee 2025-05-10)   if (!validateEmail(email)) {

Blame a Specific Line Range

# Lines 10-30 only
git blame -L 10,30 src/auth/login.ts

# From a function name
git blame -L '/function login/,/^}/' src/auth/login.ts

Ignore Whitespace Changes

# Skip commits that only changed whitespace
git blame -w src/auth/login.ts

Detect Code Movement

# Detect lines moved within the same file
git blame -M src/auth/login.ts

# Detect lines moved from other files
git blame -C src/auth/login.ts

# More aggressive detection (across the entire repo)
git blame -C -C -C src/auth/login.ts

Blame at a Specific Revision

# Blame the file as it was 3 commits ago
git blame HEAD~3 -- src/auth/login.ts

# Blame at a specific tag
git blame v2.0.0 -- src/auth/login.ts

Ignoring Bulk Reformatting Commits

When a commit reformats many files (e.g., running Prettier), it pollutes blame output. Use a .git-blame-ignore-revs file:

# .git-blame-ignore-revs
# Prettier reformatting
abc1234567890

# Configure git to use it
git config blame.ignoreRevsFile .git-blame-ignore-revs

Alternative: git log -p

For deeper history of a specific section:

# Full history of changes to specific lines
git log -p -L 10,20:src/auth/login.ts