Text Diff Checker
Compare two texts line by line — every addition and removal highlighted.
Nothing leaves your device. The comparison runs in JavaScript on this page.
About this tool
This free text compare tool shows exactly what changed between two versions of a text.
Paste the original on the left and the new version on the right, hit Compare, and every
removed line is marked in red while every added line is marked in green, aligned
side by side. It uses a longest-common-subsequence (LCS) algorithm — the same approach
behind git diff — so moves and rewrites are matched sensibly rather than
shown as wholesale deletion plus re-adding.
Common uses: comparing two versions of a contract or article before sending, checking what a colleague changed in shared copy, verifying code snippets or config files, and spotting accidental edits in translated text. Options let you ignore case or whitespace-only differences when those don't matter. Everything runs entirely in your browser — your text is never uploaded, stored or sent anywhere.
Frequently asked questions
Is my text sent to a server?
No. The comparison runs entirely in your browser with JavaScript — nothing you paste is transmitted or stored, so comparing confidential documents and source code is safe.
What do the colors mean?
Red lines exist only in the left (original) text and were removed. Green lines exist only in the right (changed) text and were added. Lines that match exactly are shown unmarked.
Can it compare code as well as prose?
Yes. The diff works line by line on any plain text, so source files, config files, JSON, and legal drafts all work. For very large files (tens of thousands of lines) the browser may slow down — split the input if that happens.
Does whitespace matter?
Yes, by default every space counts, because in code and contracts a changed indent can be meaningful. Normalize the texts first (trim trailing spaces) if you want to ignore those differences.