What does detached HEAD mean in Git, and how can I keep new work?

Detached HEAD means HEAD points directly to a commit rather than referring to a named branch. That can happen when you check out a commit ID or a tag. It is a Git state. The important distinction is that a new commit made in this state is not added to a named branch, so it may be hard to find after you move elsewhere.[S1]

If you are still at the commit containing the work you want, give that commit a branch name before leaving it. For example, git switch -c keep-work creates a branch at the current commit.[S1]

If you are still at that commit, create a branch there now: git switch -c keep-work. Choose a descriptive name if you prefer, such as experiment-notes. The key is to create the branch while the wanted commit is current; the new branch gives that commit a name you can return to.[S1]

For example, suppose your commit is a hypothetical change to a draft parser experiment. While that commit is checked out, run git switch -c parser-experiment. This preserves a reference to that commit; it does not say whether the example change has been tested or merged. If you have several detached commits, make sure the current commit is the one you intend to preserve: the command names the current point, not a different commit you have in mind.

There may be. The Git checkout manual describes using the reflog to recover the object name of a commit made while detached.[S1] The documentation available here does not give the exact commands or establish that every past commit can be recovered, so a particular result cannot be promised. If you locate the wanted commit, preserve it by creating a branch at that commit. If you are unsure which entry is yours, avoid guessing and consult Git’s documentation or someone familiar with your repository before changing state.

Use this short sequence:

1. Decide which commit contains the work you want to keep.
2. If that commit is current, create a branch there with git switch -c keep-work (replace keep-work with your chosen name).[S1]
3. If you already moved away, use the reflog as a possible way to find the detached commit’s object name; recovery is not guaranteed.[S1]
4. Once you have identified the intended commit, give it a branch name rather than relying on remembering an unnamed commit.

Run the branch-creation command while the wanted commit is current. This guide covers preserving a reference to a commit; it does not verify the contents of your changes or establish whether they are suitable to share.