The HEAD normally points at a branch, which points at a commit. In a detached HEAD, HEAD points directly at a commit instead of a branch, which happens when you check out a tag, a specific commit or a remote branch. New commits are then not on any branch.
Before you start
You should be comfortable with commits and branches. This article covers the detached state and how to recover.
Step-by-step walkthrough
Step 1: Recognize the state
Checking out a commit hash, a tag or origin/main detaches HEAD, and Git prints a warning. You can inspect and build in this state safely; nothing is wrong until you commit.
Step 2: Commits here are unreferenced
A commit made in a detached HEAD is reachable only by HEAD, not by a branch. Switching branches leaves those commits unreferenced, so they can eventually be garbage-collected. They are not lost immediately, but they are not protected.
Step 3: Create a branch to keep them
Before leaving, create a branch at the current commit: git switch -c keep-work (or git branch keep-work). That gives the commits a branch to live on. If you already left, the reflog still points at them, and you can create a branch from the reflog entry.
Worked scenario
The commit is kept by branching before leaving.
git switch --detach v1.2.3 # detached HEAD at the tag
git switch -c fix-on-v1.2.3 # attach the work to a new branchWalk through the example
Detaching lets you start from the tagged commit. Committing there produces a commit not on any branch, so git switch -c immediately creates a branch pointing at it. Now the work is safe and can be pushed or merged normally.
Common mistake
Making commits in a detached HEAD and then switching branches, leaving the commits unreferenced, which feels like losing work. Another is panicking: the reflog retains the commits for a while, so recovery is usually possible.
Verify the behavior
Detach at a commit, make a commit, and confirm git branch does not list it. Switch away and confirm the commit is unreferenced, then recover it from git reflog and create a branch.
Interview exercise
Is a detached HEAD an error?
Answer and reasoning
No. It is a normal state for inspecting a specific commit, tag or remote branch. It becomes a problem only if you commit and then leave without creating a branch, because the commits are not on a branch. In that case the reflog still references them, so you can create a branch and recover.
Continue learning
Compare recovery in Reflog recovery and history in Revert vs reset. Read the Git detached HEAD documentation and try the Git interview questions.