Free Text Difference Checker Online
Free Text Difference Checker Online is a free online tool by US AI. Paste the original text on the left and the modified version on the right — every difference is highlighted instantly: added lines in green, removed lines in red, with a summary of how many lines changed. Developers compare code revisions, writers check edited drafts, and students verify quoted passages. It runs completely in your browser — no signup, no download, works on mobile and desktop.
📖 How to use
- Paste the original text into the left box and the modified text into the right box.
- Optionally tick “ignore case” or “ignore whitespace”, then press Compare.
- Review the highlighted diff and copy the unified diff if you need it — nothing leaves your device.
✨ Why use this tool?
US AI's free diff checker uses a real longest-common-subsequence algorithm in your browser — no server, no waiting, no privacy risk. It is fast, private and 100% free forever. Pair it with our plagiarism checker and summarizer for the full text toolkit. Bookmark this page and share it with anyone who edits documents.
❓ FAQs
How does the comparison work? The tool splits both texts into lines and runs a longest-common-subsequence (LCS) diff — the same family of algorithm behind professional diff tools — then highlights added lines green and removed lines red.
Is my text uploaded anywhere? No. The entire comparison happens locally in your browser with JavaScript. Your text never leaves your device.