Question 1

What is a diff and how do I read it?

Accepted Answer

A diff (difference) highlights what changed between two texts. Lines marked with + exist only in the right/new text (additions); lines marked with - exist only in the left/old text (deletions); unmarked lines are unchanged context. The diff checker shows changes at line level with optional character-level highlighting for precise edit location.

Question 2

Can I compare code files, not just plain text?

Accepted Answer

Yes. Paste any text including source code, JSON, YAML, HTML, SQL, or configuration files. The diff is purely text-based — it compares line by line regardless of content type. For structured JSON comparison, the JSON workspace at /json has a dedicated JSON diff mode that understands JSON structure.

Question 3

What does 'ignore whitespace' do?

Accepted Answer

When enabled, whitespace-only differences (extra spaces, tab vs space, trailing spaces) are ignored and do not appear as changes. This is useful when comparing code that has been reformatted or when whitespace normalisation differences should not count as meaningful changes.

Question 4

Is my text private?

Accepted Answer

Yes. Comparison runs entirely in your browser using JavaScript. Neither the left nor the right text is sent to any server. You can use the diff checker with sensitive content such as config files, credentials, or proprietary code.

Diff Checker

About this diff checker

Side-by-side vs unified diff

Common use cases