How to fix ! [rejected] main -> main (fetch first) error: failed to push some refs in Git

First, download the new commits from the remote repository without modifying your local branch:

git fetch origin

This updates your remote-tracking branches (like origin/main) so you can see what changed.

Before merging, check what commits exist on the remote that you don't have:

git log HEAD..origin/main --oneline

This shows commits on origin/main that aren't in your local branch. Understanding these changes helps you anticipate potential conflicts.

The simplest approach is to merge the remote changes into your local branch:

git pull origin main

Or if you've already fetched:

git merge origin/main

This creates a merge commit combining both sets of changes. If there are conflicts, Git will pause and ask you to resolve them manually.

For a cleaner, linear history, you can rebase your commits on top of the remote changes:

git pull --rebase origin main

Or if you've already fetched:

git rebase origin/main

This replays your local commits on top of the remote's latest state. The result is a straight-line history without merge commits.

If Git reports conflicts during merge or rebase, you'll need to resolve them:

1. Open the conflicting files and look for conflict markers (<<<<<<<, =======, >>>>>>>)
2. Edit the files to keep the correct content
3. Stage the resolved files: git add <file>
4. For merge: git commit to complete the merge
5. For rebase: git rebase --continue to proceed

If you get stuck during a rebase, you can abort with git rebase --abort.

Once you've integrated the remote changes, push again:

git push origin main

The push should now succeed because your local branch includes all the remote commits plus your own.