Online Diff Tool — Compare Two Texts

Online diff — compare two texts in your browser

This is a free online diff tool for prose, paragraphs and any string text. Paste original on the left, changed on the right, click Compare — every added word is highlighted green, every deleted word red, every changed word is shown both ways. Everything runs locally in JavaScript so even sensitive content (contracts, drafts, NDAs, internal docs) stays on your device.

Word diff vs line diff — what this tool does

This is a word-level diff, also called a word diff. It catches small edits inside long sentences without flagging the entire line as changed. That's different from a line diff (what git diff and code review tools use), which marks whole lines as added/removed. For natural-language editing — proofreading, copy revision, contract comparison, AI-output comparison — word-level diffing is usually what you want.

Common use cases for the diff tool

• Proofreading edits — see exactly what your editor changed in your draft
• Comparing AI outputs — diff two LLM responses to the same prompt
• Contract revision tracking — see what the other party changed in v2 vs v1
• String comparison for debugging — why is this string slightly different from what the API expected?
• Translation review — compare an updated translation against the previous version
• Commit message review — quick check before you hit send

Side-by-side vs inline view

Toggle the view at the top of the result:

• Side-by-side — original left, changed right, easy for scanning whole sections side by side. Best for long-form content.
• Inline — single combined stream with red strikethrough for deletions and green underlines for additions. Best for proofreading sequential edits or short snippets.

Privacy & how it works

The diff algorithm runs entirely client-side via JavaScript. Neither the original nor the compared text is uploaded, logged, cached or sent anywhere. The tool doesn't even keep a history — refresh the page and everything is gone.