How to fix error: failed to push some refs to 'origin' in Git

The most common fix is to fetch and merge remote changes before pushing:

git pull origin <branch-name>

For example, if you're on the main branch:

git pull origin main

This fetches the remote changes and merges them with your local commits. If there are no conflicts, you can then push:

git push origin main

If you prefer a linear commit history without merge commits, use rebase instead:

git pull --rebase origin <branch-name>

This replays your local commits on top of the remote commits. After rebasing:

git push origin <branch-name>

When to use rebase:
- Working on a feature branch
- You want a clean, linear history
- Your local commits haven't been shared with others yet

Ensure your local branch name matches the remote. GitHub changed the default branch from master to main:

# Check your current branch
git branch

# Check remote branches
git branch -r

# If you need to push to 'main' instead of 'master':
git branch -M main
git push -u origin main

If you're on master locally but the remote only has main:

git checkout master
git branch -M main
git push origin main

Warning: Force pushing overwrites remote history. Only use this when you understand the consequences.

If you intentionally rewrote history (via rebase or amend) and need to update the remote:

# Safer option - fails if someone else pushed
git push --force-with-lease origin <branch-name>

# Destructive option - use with extreme caution
git push --force origin <branch-name>

Never force push to shared branches like main or develop unless you've coordinated with your team. This can cause others to lose their work.

If git pull results in conflicts, you'll need to resolve them:

# See which files have conflicts
git status

# Open conflicting files and resolve manually
# Look for markers: <<<<<<<, =======, >>>>>>>

# After resolving, stage the files
git add <resolved-file>

# Complete the merge
git commit

# Now push
git push origin <branch-name>

To abort the merge and return to the previous state:

git merge --abort

If pull and push still fail, the remote may have restrictions:

GitHub/GitLab branch protection:
- Go to repository Settings > Branches
- Check if the branch requires pull requests
- You may need to create a PR instead of pushing directly

Pre-receive hooks:
- Server-side hooks can reject pushes for various reasons
- Check with your repository administrator

Azure DevOps policies:

# If policies require PRs, create a branch and push there
git checkout -b feature/my-changes
git push -u origin feature/my-changes
# Then create a PR through the web interface