How to use the Diff Checker
- Paste the original text on the left and the changed text on the right.
- Differences are highlighted as you type: green for added, red for removed.
- Changed lines also highlight the exact words that differ.
- Use “Ignore case” or “Ignore whitespace” to hide changes that do not matter.
How the comparison works
The checker finds the longest common subsequence of lines between the two texts — the same idea behind git diff. Lines that exist in both, in order, are unchanged; everything else is an addition or a removal. When a removed line is followed by an added one, the pair is treated as an edit and the changed words are highlighted inside it.
Getting a clean comparison
- JSON: run both sides through the JSON Formatter with “Sort keys” on first, so key order and indentation do not show up as changes.
- Prose: turn on “Ignore whitespace” to skip reflowed spacing.
- Lists: if order does not matter, sort or de-duplicate both lists first.
Frequently asked questions
Is it safe for confidential documents or code?
Yes. Both texts are compared in your browser and never uploaded, which makes it suitable for contracts, credentials-adjacent config and unreleased code.
Can I compare two files?
Yes — drop a text file onto either side, or paste its contents.
Why does a whole block show as changed?
If most lines in a region differ, the tool shows it as removed and re-added rather than guessing at alignments. Very large inputs with little in common are also compared as blocks to keep your browser responsive.