Compare Two Texts and Find the Differences
Paste two versions and see exactly what changed, line by line and word by word. Free, instant, and nothing is uploaded.
Original
Changed
How to use the Diff Checker
- 1
Paste the original on the left and the changed version on the right.
- 2
Differences highlight as you type — changed words are marked within each line.
- 3
Switch between side-by-side and unified, or tick "Only changes" to hide the identical parts.
Frequently asked questions
How big a file can it compare?
Comfortably tens of thousands of lines. It uses Myers' diff algorithm, whose cost scales with the number of differences rather than the size of the files — so two large but similar documents compare almost instantly. Five thousand lines with three changes takes about five milliseconds.
Can it show which words changed, not just which lines?
Yes. When a line has been edited rather than replaced outright, the changed words are highlighted within it. If two lines are too dissimilar to be a sensible pairing, the whole line is marked instead — highlighting every word would be noise.
Is my text sent anywhere?
No. The comparison runs in your browser, so you can safely paste configuration files, contracts, source code or anything else confidential. Disconnect from the internet and it still works.
Is my data uploaded to a server?
No. Every tool on this site runs entirely inside your browser using JavaScript. Your input never leaves your device and is never sent over the network, which means it is safe to paste production data, API responses and tokens.