Sync a GitHub fork with its upstream repository

Add the original repository as an upstream remote, fetch it, and integrate its branch into the branch you want to update. Push the result to origin, which should point to your fork. Check both URLs before changing anything.

Configure the upstream remote

git remote -v
git remote add upstream https://github.com/original-owner/repository.git

Add it only once. If the name already exists, inspect its URL and correct it deliberately instead of adding another remote. Replace the example URL with the actual original repository.

Update your fork's main branch

With local work saved:

git fetch upstream
git switch main
git merge upstream/main
git push origin main

Use the actual upstream branch name. The merge fast-forwards when possible; if the histories have diverged, it can create a merge commit or report conflicts. For a fork branch intended to remain an untouched mirror, git merge --ff-only upstream/main refuses divergence so you can investigate instead of creating a merge automatically.

If origin/main contains other commits not in your local branch, the push may be rejected. Fetch and reconcile that work rather than forcing over it.

Use GitHub's Sync fork action

On the fork's repository page, choose Sync fork and then Update branch when offered. Having commits of your own does not automatically make web synchronization impossible. If there are merge conflicts, GitHub prompts you to resolve them, potentially through a pull request or local workflow.

After updating through the website, fetch your fork locally so your remote-tracking refs reflect the change. The website does not update a checkout on your computer.

Update a feature branch

git fetch upstream
git switch feature-x
git rebase upstream/main

A rebase can keep a private feature branch linear, but it rewrites its commits. If the branch is already published or used by others, follow the team's policy; a merge may fit better. Publishing a rewritten branch can require a carefully reviewed lease-protected update.

FAQ

Why does Git report unrelated histories?

Verify the remote URL and available history. An ordinary fork relationship should have shared ancestry. A shallow clone or a repository created independently can obscure that relationship; do not automatically add --allow-unrelated-histories to bypass the investigation.

Can synchronization be scheduled?

A scheduled workflow can fetch, integrate, and push with suitable permissions. It still needs conflict handling, failure reporting, and a decision about branches with local work. Treat a community template as code to review, not as a guarantee that every fork stays synchronized safely.

What if upstream renamed its default branch?

Fetch the new branch and inspect git remote show upstream. git remote set-head upstream -a updates the local upstream/HEAD symbolic ref; it does not rename your local branch or rewrite its tracking configuration. Update those separately if needed, and use the correct new branch name in future synchronization commands.

See GitHub's fork synchronization guide, git-remote, and git-merge.