Merging code is routine. Undoing a merge usually isn’t, until it suddenly is.

A wrong branch, an incomplete feature, or a missed conflict can all lead to a bad merge. When that happens, knowing how to undo a merge in Git cleanly can save your branch and your team’s time.

What Does “Undo Merge Git” Really Mean?

Undoing a merge depends on timing. Git offers different tools depending on whether the merge:

• hasn’t been committed
• is committed but not pushed
• is already pushed to GitHub

Using the wrong approach can rewrite history or break collaboration, so context matters.

Cancel a Merge Before It’s Committed

If a merge is in progress and conflicts aren’t resolved yet, Git lets you stop immediately.

git merge --abort

This command cancels the merge and returns your branch to its original state.

Use this when:

• you merged the wrong branch
• conflicts look risky
• you want to rethink the merge strategy

This is the safest way to undo a merge because no commit is created.

Undo a Merge Commit Locally (Not Pushed)

If the merge commit exists but hasn’t been pushed, you can remove it:

git reset --hard HEAD~1

This completely deletes the merge commit.

Important:

Only do this on branches no one else depends on. Resetting rewrites history.

Revert a Merge on GitHub

Once a merge is pushed, resetting is no longer safe. The correct option is to revert a merge on GitHub.

Git Revert Commit Merge

git revert -m 1 <merge_commit_hash>

The -m 1 flag tells Git which parent branch to keep.

This creates a new commit that undoes the merge without altering history. This is why it’s commonly called:

• GitHub rollback merge
• Revert merge GitHub

GitHub’s Revert button does the same thing, making it the safest option for shared branches.

Why Bad Merges Still Happen

Most merge rollbacks aren’t Git problems, they’re review problems.

Common causes:

• oversized pull requests
• rushed approvals
• missing context during review
• unresolved conflicts discovered too late

PRFlow helps reduce these risks by promoting smaller, focused pull requests and clearer review checkpoints, so fewer merges need undoing in the first place.

Final Takeaway

Knowing how to undo merge Git is essential. Knowing which method to use is what keeps your repo stable.

Cancel early when you can.

Revert when the merge is already shared.

Avoid rewriting history on team branches.

Undoing a merge should be a recovery tool, not a routine workflow.