Text Diff / Compare

What this text-compare tool does

Paste two versions of any text and this tool shows you exactly what changed — line by line, with removed lines marked in red and added lines in green. It uses a proper longest-common-subsequence (LCS) diff, the same approach version-control systems use, so it aligns matching lines correctly instead of just comparing position-for-position.

How to use it

Put the original text on the left and the changed text on the right. The differences appear instantly below, and a counter shows how many lines were added and removed. Use Swap sides to flip the comparison, and keep Ignore leading/trailing spaces on if you do not care about indentation changes. Everything is computed in your browser — your text is never uploaded, which matters for contracts, code, and private documents.

Where a diff helps

Proofreading and editing: see precisely what an editor or co-author changed. Code review: compare two snippets before committing. Config and data: spot the one line that differs between a working and a broken file. Contracts and policies: confirm which clauses moved between revisions.

Reading the output

Lines with no marker are unchanged. A red - line existed only in the original; a green + line exists only in the changed version. A modified line shows as a red line immediately followed by a green line.

Frequently asked questions

Word-by-word or line-by-line? Line by line, which is the most readable for documents and code. Whitespace-only differences can be ignored with the toggle.

Is there a size limit? Very large inputs fall back to a faster simple comparison to stay responsive; normal documents use the full LCS diff.

Is my text private? Completely — the comparison runs in your browser and nothing is sent anywhere.