How to fix error: The branch 'feature' is not fully merged. If you are sure you want to delete it, run 'git branch -D feature' in Git

First, understand what Git is comparing against. The -d flag only checks if the branch is merged into HEAD:

# See your current branch
git branch --show-current

# Or see all branches with current highlighted
git branch -v

If you're trying to delete a feature branch that was merged into main, make sure you're actually on main:

git checkout main
git branch -d feature-branch

This often resolves the warning immediately.

If the merge happened on the remote (via pull request), your local branch needs to be updated:

# Fetch all remote changes
git fetch origin

# Update your local main to match remote
git checkout main
git pull origin main

# Now try deleting again
git branch -d feature-branch

The warning appears because your local main doesn't have the merge commit yet. After pulling, Git can see that the feature branch's commits are now part of main.

Before force-deleting, confirm whether the commits are truly safe:

# See commits on the branch you want to delete
git log feature-branch --oneline

# Check if those commits exist in main
git log main --oneline | head -20

# Better: check if the branch is an ancestor of main
git merge-base --is-ancestor feature-branch main && echo "Safe to delete"

# Or see commits in feature-branch but NOT in main
git log main..feature-branch --oneline

If git log main..feature-branch shows no commits, the branch's work is already in main, and it's safe to delete. If it shows commits, those would be lost.

If you use "Squash and merge" on GitHub/GitLab, the original commits get combined into a new single commit with a different hash. Git can't tell they're "the same" work.

Option 1: Force delete after confirming the PR was merged

# If you've verified the PR is merged on GitHub/GitLab
git branch -D feature-branch

Option 2: Use the merged branch as reference

# Delete relative to main, not HEAD
git checkout main
git pull origin main
git branch -d feature-branch

Option 3: Check the PR status first

# With GitHub CLI
gh pr view feature-branch --json state,mergedAt

For teams that regularly use squash merges, force-deleting with -D after confirming the PR is merged is the standard workflow.

Similar to squash merges, "Rebase and merge" rewrites commits with new hashes. The content is identical, but Git sees different commit IDs.

# After a rebase-merge, you'll need to force delete
git branch -D feature-branch

# To verify the changes made it in, compare trees
git diff main feature-branch

# If the diff is empty or minimal, the changes are integrated

The key insight: after a rebase-merge, your local feature branch and the rebased version on main have the same changes but different history. Git's merge detection doesn't help here.

If you've verified the work is merged (or you intentionally want to discard it), use the uppercase -D flag:

# Force delete - bypasses the merge check
git branch -D feature-branch

When it's safe to force delete:
- The PR/MR was merged (check on GitHub/GitLab)
- You ran git diff main feature-branch and it's empty
- You intentionally want to abandon this work
- The branch was merged but using squash/rebase strategies

When you should NOT force delete:
- You haven't checked if the work was merged
- The branch contains uncommitted experiments you might want
- Other team members might be depending on this branch

After pull requests are merged, you may have many local branches to clean up:

# First, update all remote tracking info
git fetch --all --prune

# See which local branches are tracking deleted remotes
git branch -vv | grep ': gone]'

# Delete all branches whose upstream is gone
git branch -vv | grep ': gone]' | awk '{print $1}' | xargs git branch -D

Or use Git's built-in cleanup for merged branches:

# Delete all local branches already merged into main
git checkout main
git branch --merged | grep -v "^*" | grep -v "main" | xargs -n 1 git branch -d

Note: This uses -d (lowercase) so truly unmerged branches will be skipped with warnings.