git merge vs git rebase: differences and when to use each

git merge combines two branches by creating a merge commit; existing commits stay untouched. git rebase replays your branch's commits on top of another branch, producing a straight line of new commits with new hashes. Merge is safe for shared branches; rebase gives a cleaner history but must not be used on commits others have already pulled.

Same branches, two results

git init -q -b main repo && cd repo
echo base > f && git add f && git commit -qm "base"
git switch -q -c feature && echo feat > g && git add g && git commit -qm "feature work"
git switch -q main && echo fix > h && git add h && git commit -qm "fix on main"
git branch -q feature-copy feature
echo "--- merge:"
git merge -q --no-edit feature && git log --oneline --graph
git reset -q --hard HEAD~1
echo "--- rebase:"
git switch -q feature-copy && git rebase -q main && git log --oneline --graph

--- merge:
*   da13255 Merge branch 'feature'
|\
| * d2e54c4 feature work
* | 249e3b5 fix on main
|/
* 350f8df base
--- rebase:
* 4f9e7f7 feature work
* 249e3b5 fix on main
* 350f8df base

Criterion by criterion

Rule of thumb

Rebase your local, unpublished work onto the latest main (git pull --rebase, git rebase main) to keep history tidy. Merge when integrating a branch that other people use, or when you want the merge to be visible in history.