Free Diff Checker — Compare Text Online
Paste two versions of a text and see the differences side by side. Comparison runs locally — nothing is uploaded.
Frequently Asked Questions
How does the diff algorithm work?
The tool computes the longest common subsequence (LCS) of lines between the two texts — the same core idea used by git and classic diff utilities. Lines only in the original are marked removed (red); lines only in the changed version are marked added (green).
Is my text sent to a server?
No. The comparison runs entirely in your browser with JavaScript. It is safe to diff confidential documents, contracts, or source code.
Can I ignore whitespace differences?
Yes — check "Ignore leading/trailing whitespace" and lines are compared after trimming, so indentation-only changes are not flagged.
Is there a size limit?
Texts up to a few thousand lines each compare instantly. For very large inputs the tool automatically switches to a faster line-by-line comparison to stay responsive.