Diff

You might say

Show me exactly what changed this time—what lines were added and what lines were removed.

See exactly what changed between two statesA diff shows added, removed, and modified lines between the working tree, staged changes, commits, or branches. Read it before committing and reviewing so accidental edits, secrets, and unrelated changes are caught early.

Know first

Git Commit

Before changesButton text− Click me

→

After changesButton text＋ Start now

git diff

Diff is a list of changes: red minus signs indicate deleted content, and green plus signs indicate new content. Read it over before submitting to make sure there are no accidentally deleted, debugged content or keys.

When to use it

Review work before a commit
Compare two branches or commits
Understand a pull request
Find an accidental or missing change

When NOT to use it

Review only the filenames and skip the actual lines
Assume a small diff has a small product impact
Include formatting changes that hide the real edit
Copy secrets into a diff shared outside the team

Anatomy

      📄 index.html
      @@ -12,5 +12,5 @@
      - 
      + 
    

Which file does this change belong to? One file and one section.

@@ -12,5 +12,5 @@: Change near line 12

Red with - sign: lines that existed in the old version and deleted in the new version

Green with a + sign: extra lines in the new version

Variants

git diff

Check what has been changed in the workspace relative to the staging area

git diff --staged

Review after add and before commit

git diff commits

git diff HEAD~1 HEAD

Review specific changes from the most recent commit

git diff main..feat

git diff main..feat/dark-mode

Before merging, check how far ahead the branch is

Typical use cases

Pre-commit review

zsh — my-first-page

$ git diff diff --git a/index.html b/index.html @@ -12,5 +12,5 @@ - + The red band - is deleted, the green band + is added

Pull request

zsh — my-first-page

$ git diff HEAD~1 HEAD --stat index.html | 10 ++++++---- style.css | 12 ++++++++++++ 2 files changed, 18 insertions(+), 4 deletions(-) $ git diff HEAD~1 HEAD Check the line-by-line details again to confirm the content of this round of AI modifications

Bug investigation

ConversationCommits 3Checks ✓Files changed 2

📄 index.html +18 −4

@@ -12,5 +12,5 @@
- 
+ 

Release comparison

🤖 AI finishes a round of changes → 🔍 review git diff line by line → ✅ git commit record