Text Diff Checker Text
Compare two blocks of text and see exactly what changed, line by line.
Text Diff Checker is a free online tool that compare two blocks of text and see exactly what changed, line by line. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Text
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- None — it just works
- Works offline
- Yes, after the first visit
About Text Diff Checker
A line-level diff using the classic longest-common-subsequence approach. Both sides stay in your browser, which makes this safe for contracts, configs and anything else you would rather not paste into a stranger’s server.
How to use it
- Everything text diff checker needs is on this page.
- Your input is processed locally and discarded when you close the tab.
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
Questions
What kind of diff is this?
Line-level, using the longest-common-subsequence algorithm — the same approach behind `diff` and Git. A changed line shows as one removal plus one addition rather than a character-level highlight.
Is it safe to paste confidential text?
Yes, and that is the main reason to use this one. Both sides are compared in your browser; nothing is transmitted. Most online diff tools post your text to a server, which is a poor idea for contracts, configs and credentials.
Why is there a 4,000-line limit?
The algorithm builds a comparison matrix, so memory grows with the two lengths multiplied together. Beyond a few thousand lines a browser tab would stall — use a desktop diff tool for anything larger.