Git: HEAD vs Working Tree vs Index (Staging Area)
Understand the key differences in Git between HEAD (pointer to current commit), working tree (editable files on disk), and index/staging area (snapshot for next commit). Learn workflow, commands like git status, git add, and common confusions like detached HEAD.
In Git, what is the difference between HEAD, the working tree, and the index (staging area)? Are they all names for different branches?
I read this explanation: > A single git repository can track an arbitrary number of branches, but your working tree is associated with just one of them (the “current” or “checked out” branch), and HEAD points to that branch.
Does this mean that HEAD and the working tree always refer to the same thing?
In Git, HEAD points to the current commit or branch tip you’re working on, the working tree holds your actual files on disk (including any modifications), and the index (or staging area) is a snapshot of changes ready for the next commit. No, they’re not different branches—branches are just lightweight pointers to commits, while these three represent distinct states in your repo: a pointer (HEAD), your editable files (working tree), and staged changes (index). That quote you read is mostly right but misses a key nuance: HEAD and the working tree don’t always match, since your files can have unstaged or uncommitted changes diverging from what HEAD references.
Contents
- What is HEAD in Git?
- Understanding the Working Tree
- The Index (Staging Area) in Git
- Key Differences: HEAD vs Working Tree vs Index
- The Git Workflow: Changes Flow
- Common Confusions and That Quote
- Sources
- Conclusion
What is HEAD in Git?
Think of HEAD as Git’s way of saying, “This is where I am right now.” It’s a special pointer—usually stored in .git/HEAD—that references the latest commit on your current branch. Switch branches with git checkout or git switch, and HEAD moves with you to point at that branch’s tip.
But here’s where it gets interesting: HEAD can detach. Run git checkout <commit-hash>, and it points directly to a specific commit, not a branch. No new branch created—just you exploring history. The official Git book nails this: HEAD isn’t a branch itself; it’s what tells Git which snapshot is active.
Why care? Commands like git log, git diff HEAD, or git reset HEAD all revolve around it. Mess up? git reset --hard HEAD wipes changes back to that point. Simple, but powerful.
Understanding the Working Tree
Your working tree (or git working tree) is dead simple: the files and folders in your repo directory that you can actually edit in your IDE or vim. It’s what you see when you ls or open the folder.
Fresh clone? The working tree matches HEAD exactly—clean and pristine. Tweak a file? Now it’s “dirty.” Git spots changes not staged for commit via git status. Untracked files? They’re in the working tree too, but ignored until git add.
The catch: the working tree doesn’t automatically sync with HEAD or anywhere else. It’s your sandbox. As LinuxHint explains, it’s on-disk reality versus Git’s abstract pointers.
The Index (Staging Area) in Git
Enter the index, aka staging area or git index—Git’s prep zone for commits. It’s a binary file (.git/index) holding a snapshot of your next commit. Empty at first? git add <file> copies changes from the working tree into it.
Git stage something, and git status shows it as “staged.” Commit with git commit, and bam—the index becomes a new commit, HEAD advances. Skip staging? Changes stay in the working tree, ignored.
Pro tip: git diff --staged peeks at index vs HEAD; git diff shows working tree vs index. The Pro Git docs call it “a snapshot of files that will be committed next.” Not magic, just selective prep.
Key Differences: HEAD vs Working Tree vs Index
| Concept | What It Is | File Location | Command Interaction |
|---|---|---|---|
| HEAD | Pointer to current commit/branch tip | .git/HEAD (ref) |
git log HEAD, git reset HEAD |
| Working Tree | Your editable files on disk | Repo root folder | Modified by edits; git status checks |
| Index/Staging | Staged snapshot for next commit | .git/index |
git add populates; git commit consumes |
They’re not branches—branches like main or feature are just files in .git/refs/heads/ pointing to commits. HEAD might point to one, but the working tree and index? Totally separate beasts. They align only on a clean repo.
Git head queries spike because folks confuse it with the tree—it’s not. Same for git index lock errors when staging clashes.
The Git Workflow: Changes Flow
Picture this flow—it’s Git’s heartbeat:
- Start clean: Working tree = index = HEAD commit.
- Edit files: Working tree diverges.
git add: Copy to index (now staged).git commit -m "msg": Index -> new commit, branch/HEAD advances.- Repeat.
Stuck? git restore --staged <file> unstages; git restore <file> reverts working tree to index; git reset HEAD <file> unstages and reverts.
Nulab’s guide shows how HEAD shifts on branch switches, but your index and tree stay put until committed.
And git status? It diffs all three states. Genius.
Common Confusions and That Quote
Back to your quote: “Your working tree is associated with just one [branch], and HEAD points to that branch.” Spot on for clean repos, but…
Does HEAD and working tree always mean the same? Nope. Edit a file—working tree changes, HEAD doesn’t budge until commit. Stage half your edits? Index partial, working tree full, HEAD old.
Detached HEAD? Working tree reflects that commit, but no branch moves on commit—risky for new work.
Git reset HEAD~1? Backs up HEAD, but tree and index? Untouched unless --hard. People trip here constantly.
They’re linked, not identical. Run git status—it screams the diffs.
Sources
- Git Book - Recording Changes to the Repository
- LinuxHint - Difference Between HEAD, Working Tree, and Index in Git
- Nulab - Pointing to Branches
Conclusion
Mastering HEAD, working tree, and index (staging area) unlocks Git’s power—they’re your repo’s three states, not branches or synonyms. Keep 'em in sync with git status, stage smartly with git add, and commit confidently. Next time git status nags about unstaged changes, you’ll know exactly what’s up. Experiment in a test repo—git init demo; cd demo—and watch the magic.