Comparing Branches

Beyond comparing individual files, Git lets you compare entire branches and commits — useful for reviewing what a feature branch adds before merging it.

Compare Two Branches

Show changes that are in feature/dashboard but not in main:

git diff main..feature/dashboard

Show changes that are in main but not in feature/dashboard:

git diff feature/dashboard..main

Three-Dot Diff — Changes Since the Branch Forked

The three-dot syntax compares feature/dashboard against the common ancestor of both branches. This shows only the changes made on feature/dashboard, ignoring any new commits on main since the branch was created:

git diff main...feature/dashboard

This is the format GitHub uses to display pull request diffs.

Compare a Branch Against Remote

See what's in origin/main that you haven't pulled yet:

git diff main..origin/main

Compare Two Commits

Find the hashes with git log --oneline, then:

git diff a3f6f1c d1e8f91

Compare a Commit to HEAD

git diff a3f6f1c HEAD

Show Only the Files That Changed Between Two Commits

git diff --name-only a3f6f1c d1e8f91

Show Stats for a Comparison

git diff --stat main..feature/dashboard

Output:

 src/dashboard.py | 45 +++++++++++++++++++++++++++
 tests/test_dashboard.py | 20 ++++++++++++
 2 files changed, 65 insertions(+)

tip

Use git diff main...feature/dashboard (three dots) when reviewing a pull request locally — it shows exactly the same changes as the GitHub PR diff.

Common Mistakes

Mixing up two-dot and three-dot diff — .. compares the tips of both branches; ... compares from the common ancestor. For code reviews, ... (three dots) is usually what you want.

Comparing the wrong direction — git diff A..B shows what B has that A doesn't. Make sure you have the branches in the right order for what you're trying to answer.

Not specifying a file when the diff is huge — narrow down large diffs with a file path: git diff main..feature/dashboard -- src/dashboard.py.

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Next Steps: What is HEAD in Git