How do I remove a single file from the staging area (undo git add)?

For newer versions of Git there is git restore --staged <file>.

When I do a git status with Git version 2.26.2.windows.1 it is also recommended for unstaging:

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)

(This post shows, that in earlier versions git reset HEAD was recommended at this point)

I can highly recommend this post explaining the differences between git revert, git restore and git reset and also additional parameters for git restore.

I think you probably got confused with the concept of index, as @CB Bailey commented:

The staging area is the index.

You can simply consider staging directory and index as the same thing.
So, just like @Tim Henigan's answer, I guess:

you simply want to "undo" the git add that was done for that file.

Here is my answer:

Commonly, there are two ways to undo a stage operation, as other answers already mentioned:

git reset HEAD <file>

and

git rm --cached <file>

But what is the difference?

Assume the file has been staged and exists in working directory too, use git rm --cached <file> if you want to remove it from staging directory, and keep the file in working directory. But notice that this operation will not only remove the file from staging directory but also mark the file as deleted in staging directory, if you use

git status

after this operation, you will see this :

        deleted:    <file>

It's a record of removing the file from staging directory. If you don't want to keep that record and just simply want to undo a previous stage operation of a file, use git reset HEAD <file> instead.

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PS: I have noticed some answers mentioned:

git checkout -- <file>

This command is for the situation when the file has been staged, but the file has been modified in working directory after it was staged, use this operation to restore the file in working directory from staging directory. In other words, after this operation, changes happen in your working directory, NOT your staging directory.

After version 2.23, Git has introduced the git restore command which you can use to do that. Quoting the official documentation:

Restore specified paths in the working tree with some contents from a restore source. If a path is tracked but does not exist in the restore source, it will be removed to match the source.

The command can also be used to restore the content in the index with --staged, or restore both the working tree and the index with --staged --worktree.

So you can invoke git restore --staged <path> and unstage the file but also keep the changes you made. Remember that if the file was not staged you lose all the changes you made to it.

When you do git status, Git tells you how to unstage:

Changes to be committed: (use "git reset HEAD <file>..." to unstage).

So git reset HEAD <file> worked for me and the changes were un-touched.

You want:

• Affect to a single file

• Remove file from staging area

• Not remove single file from index

• Don't undo the change itself

and the solution is

git reset HEAD file_name.ext

or

git reset HEAD path/to/file/file_name.ext

You need to be in the directory of the file and then type the following into the terminal

git checkout -- <file>

If you make changes to many tracked files but only want to stage a few of them, doing a

git add .

isn't always favorable (or recommended)- as it stages all the tracked files (some cases where you want to keep changes only to yourself and don't want to stage them to the remote repository).

nor is it ideal doing a bunch of

git add path/to/file1 path/to/file2

if you have a lot of nested directories (which is the case in most projects) - gets annoying

That's when Git GUI is helpful (probably only time I use it). Just open Git GUI, it shows staged and unstaged file sections. Select the files from the staged section that you want to unstage and press

Ctrl+U (for windows)

to unstage them.

My sample:

$ git status
On branch feature/wildfire/VNL-425-update-wrong-translation
Your branch and 'origin/feature/wildfire/VNL-425-update-wrong-translation' have diverged,
and have 4 and 1 different commits each, respectively.
  (use "git pull" to merge the remote branch into yours)

Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

    modified:   ShopBack/Source/Date+Extension.swift
    modified:   ShopBack/Source/InboxData.swift
    modified:   ShopBack/en.lproj/Localizable.strings

As you may notice

> Changes to be committed:
>       (use "git reset HEAD <file>..." to unstage)

You need to be in the directory of the file and then type the following into the terminal

git reset HEAD .

Assumption is that you need to reset one file only.