No upload, 100% local, no account

Text Diff

Paste two texts to compare them line by line. Added lines are green, removed lines are red. Nothing leaves your browser.

How Text Diff works

Paste two blocks of text and instantly see every addition, deletion, and unchanged line highlighted side by side. Whether you are comparing drafts, reviewing config changes, or spotting regressions in generated output, Text Diff gives you a clear, colour-coded view in seconds.

The diff uses a line-by-line longest-common-subsequence algorithm, the same family as the Unix diff utility, with additions in green, deletions in red, and unchanged lines neutral. Results update as you type.

Frequently asked questions

Are my files uploaded to a server?

No. Every operation runs inside your browser tab using JavaScript and WebAssembly. Your file is read into memory on your own device, processed there, and the result is offered as a local download. Nothing is transmitted to Sunasty or any third party. You can verify it yourself: open your browser DevTools, go to the Network tab, and watch, no request carries your file.

What diff algorithm is used?

The tool uses a line-by-line longest-common-subsequence (LCS) diff, the same family of algorithm as the Unix diff utility. Additions are shown in green, deletions in red, and unchanged lines in neutral colour.

Can I compare files instead of pasted text?

Yes, drag a plain-text file into either panel and its content is read locally by the browser's FileReader API. The file is never uploaded.

Does it work offline?

Yes, once the page has loaded. Because the processing happens on your device, you can disconnect from the network and the tool keeps working. This is the clearest proof that your data never leaves your machine.

Is it free? Do I need an account?

It is completely free and requires no sign-up. There are no watermarks, no daily limits and no tracking cookies needed to use the tool.