How to use the diff checker
- Paste the original text on the left and the changed text on the right.
- The result highlights added lines in green and removed lines in red; unchanged lines stay plain.
- Use it to compare drafts, contracts, code snippets, config files or any two blocks of text.
What a diff shows you
A "diff" compares two texts line by line and marks exactly what changed between them. It's the same idea developers use to review code, but it's just as useful for spotting edits between two versions of an essay, a contract, an email, or a list. Instead of re-reading everything and hoping you catch the change, the diff points straight to it.
Benefits
- Highlights exactly what was added, removed or unchanged between two texts, line by line.
- Works on anything — essays, contracts, emails, code, JSON or config files.
- Gives a quick summary count of additions and deletions.
- Runs entirely in your browser; nothing you compare is uploaded.
Limitations to know
- It compares line by line, not word by word within a line.
- Very large inputs can slow down since the comparison runs locally.
- It shows differences but does not merge the two versions for you.
Common mistakes to avoid
- Pasting the versions in the wrong boxes, which flips additions and removals.
- Expecting inline word-level highlighting inside a changed line.
- Comparing formatted text and forgetting invisible differences like trailing spaces.
Alternatives
To replace text across a document use Find & Replace; to tidy JSON before comparing it, use the JSON Formatter.
Last updated: August 2026 · Reviewed by the AI Toolbox editorial team.
Frequently asked questions
Is my text uploaded?
No — the comparison runs entirely in your browser. Nothing is sent anywhere.
Does it compare line by line or word by word?
It compares line by line, which is the clearest way to review edits in documents, lists and code.
Can I compare code?
Yes — it works on any plain text, including code, JSON and config files.
Is there a size limit?
It handles typical documents easily. Extremely large files may slow down since everything runs locally.