Free Diff Checker — Compare Text
Paste two versions of a document, contract, essay or code file and see exactly what changed: added lines in green, removed lines in red, with the changed words highlighted.
How to use the diff checker
- Paste the original version on the left and the new version on the right.
- Click Compare. Removed lines are shown in red with a minus sign, added lines in green with a plus sign, and the specific words that changed inside a line are highlighted.
- Use the options to ignore differences in capitalization or extra spaces at the start and end of lines.
What a diff checker is good for
A diff (short for difference) shows the minimum set of line additions and deletions that turns one text into another. This tool uses the longest-common-subsequence approach that classic Unix diff and Git are built on, so unchanged lines line up and the real edits stand out. When a removed line and an added line are close matches, it also compares them word by word so you can spot a single changed term in a long paragraph.
It is useful well beyond code. Compare two drafts of a contract to see what the other side changed, check an edited essay against the original, confirm that a config file matches production, find what changed between two versions of a policy, or verify a copied list did not lose any items. Lawyers call this redlining; programmers call it a diff; it is the same idea.
Your text is compared entirely in your browser and never uploaded, which matters when the documents are confidential. For very large files (tens of thousands of lines), a desktop tool or git diff will be faster, but for everyday documents this is instant.
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Frequently asked questions
Is my text uploaded anywhere?
No. The comparison runs in your browser; nothing is sent to a server or saved.
Can it compare Word documents or PDFs?
Copy the text out of each document and paste it in. Formatting is ignored; only the text is compared.
Why does a moved paragraph show as removed and added?
A line-based diff sees a moved block as a deletion in one place and an insertion in another. That is standard behavior for diff tools.
How large a text can I compare?
Several thousand lines work smoothly. Extremely large inputs may take a few seconds.