Diff Checker
Text toolNewCompare two blocks of text and highlight the differences.
This tool runs entirely in your browser. Your files never leave your device — nothing is uploaded.
Original
Changed
Differences
Paste text into both boxes above to see a line-by-line comparison.
Frequently asked questions
How does the diff checker compare my two texts?
It splits each text into lines and runs a longest-common-subsequence (LCS) algorithm to find the lines that stayed the same. Lines only in the original are marked as removed (red) and lines only in the changed version are marked as added (green), with a running count of each.
Is my text uploaded to a server?
No. The entire comparison runs locally in your browser using JavaScript, so nothing you paste ever leaves your device. There are no uploads, accounts, or logs, which makes it safe for confidential code, contracts, or notes.
Does it handle Windows and Unix line endings?
Yes. The tool normalises Windows-style CRLF line endings to LF before comparing, so pasting text copied from different editors or operating systems will not produce false differences. You only see real content changes, line by line.