What does diff mean in software engineering?

A diff is a detailed comparison between two versions of a file or code, showing which lines have been added (usually in green), removed (usually in red), or modified. It is the standard output from version control systems like Git when comparing changes.

How do you use diff in a sentence at work?

You can use it as a noun: 'Please review the diff before merging' or as a verb: 'Can you diff these two files to see what changed?' Both are common in tech workplaces.

Is diff formal or informal?

Diff is neutral and professional. It is the standard technical term used in code reviews, pull requests, and team discussions. It is neither overly casual nor unnecessarily formal.

What is the difference between diff and patch?

A diff is a visual comparison showing changes line-by-line. A patch is often a file that contains those changes in a format that can be applied to another codebase. All patches start with a diff, but not all diffs become patches.

Why do developers care so much about diffs?

Diffs allow developers to review exactly what changed in a pull request, catch bugs before merging, understand the impact of changes, and maintain code quality. They are central to the code review process.

Diff Meaning in Code Review: What “Check the Diff” Means

Commonness	5/5
Versatility	4/5
Formality	CasualFormalNeutral
Spoken ↔ Written	SpokenWrittenBoth
Directness ↔ Diplomatic	DirectDiplomaticDirect
Region	US and UK

Say it like this

Check the diff before merging
The diff looks good to me
Run a diff on those two files

Use it at work

Code review

The diff is small, just two files.
Can you share the diff before you push?

Debugging

Let's diff the two configs to see what changed.
The diff shows someone changed the timeout.

Asking

Can you split this PR? The diff is 2,000 lines.
Run git diff to see your changes.

Don't say this

✕I need to see the difference between these files.

✓I need to see the diff between these files.

Diff is the standard technical term for code/file comparisons; use it instead of the generic difference.

Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. Your colleague pushes code and asks you to review it. What do you say?

Can you review the diff?Can you see the differences?Can you check what changed?Can you examine the modifications?

Complete the sentence

2. Before merging any pull request, we must _______ the _______ carefully.

Spot the mistake

3. Which sentence uses 'diff' incorrectly?

The diff shows exactly what was removed and what was added.Please diff the staging and production configs.This diff is very different from the last one.I ran a diff command to compare the two versions.

Rewrite naturally

4. Rewrite in tech English: 'I want to look at the comparison between the old code and the new code to understand the changes.'

Say it out loud

Phrase 1 of 3

"Check the diff before merging"

We don't save your recording. The word check uses your browser's speech recognition.

More about diff

Real examples(3)

in a code review
"I reviewed the diff and found three bugs in the payment logic that need to be fixed."
in a standup meeting
"The diff for the database migration is pretty large, so I want to walk through it with the team."
in a pull request comment
"This diff adds too many changes at once. Can you split it into smaller, more focused commits?"

More mistakes(2)

Handle with care. Do not confuse diff (a comparison output) with difference (general concept). Diff refers specifically to the formatted comparison of file or code changes, not just any difference.

✕Did you diff the old version and new version?
✓Did you compare the old version and the new version? / What does the diff show?
Diff is primarily a noun (the output); when asking about the comparison action, use compare or ask about the diff result.
✕This diff is very different.
✓This diff shows many changes. / This is a large diff.
Avoid using diff as an adjective; use it as a noun or describe the diff itself.

Other forms(2)

diff noun
"Please review the diff before we ship this feature."
diff verb
"Let me diff these two configuration files to see what changed."

Often used with(5)

check the diff · Review the comparison output to see what changed
review the diff · Examine the diff carefully during code review
large diff · A diff with many changes, often indicating a big commit
merge the diff · Accept and integrate the changes shown in the diff
run a diff · Execute a diff command to compare files

Similar words(3)

patch · Similar context but patch often refers to a file containing changes ready to be applied
changeset · A broader term for all changes in a commit, while diff shows the detailed line-by-line comparison
delta · The difference or change between two versions, but less specific to code formatting

Questions(5)

What does diff mean in software engineering?: A diff is a detailed comparison between two versions of a file or code, showing which lines have been added (usually in green), removed (usually in red), or modified. It is the standard output from version control systems like Git when comparing changes.
How do you use diff in a sentence at work?: You can use it as a noun: 'Please review the diff before merging' or as a verb: 'Can you diff these two files to see what changed?' Both are common in tech workplaces.
Is diff formal or informal?: Diff is neutral and professional. It is the standard technical term used in code reviews, pull requests, and team discussions. It is neither overly casual nor unnecessarily formal.
What is the difference between diff and patch?: A diff is a visual comparison showing changes line-by-line. A patch is often a file that contains those changes in a format that can be applied to another codebase. All patches start with a diff, but not all diffs become patches.
Why do developers care so much about diffs?: Diffs allow developers to review exactly what changed in a pull request, catch bugs before merging, understand the impact of changes, and maintain code quality. They are central to the code review process.

New app · Free lessons