Git: What’s the index?

In a nutshell

The index is your staging area, containing all the files that have been staged from your working tree using git add <some-file>.

Where does the index fit in the Git workflow?

• You make a change.
• You stage the change to the index (git add <file>).
• You commit changes in your staging area to your local repo (git commit)
• You push the changes from your local repo to the remote repo (git push)

Other notes

More specifically, the index is a single, large, binary file in <repo>/.git/index that lists all the files in the current branch and their:

• SHA1 checksums
• Timestamps
• Filename

Sources

• What’s the difference between HEAD, working tree and index, in Git? – StackOverflow