Text Diff Checker
Paste two versions and see exactly what changed, with edited words highlighted.
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Explain what changed
Optional. Uses an AI model built into your browser, on your device, and only sees the changed lines. The comparison above works without it.
Checking what your browser can do…
Your files stay on your device
How to use it
Paste the original on the left and the new version on the right to see exactly what changed, with edited words highlighted. Your text stays on your device.
Paste the original text on the left and the changed version on the right. The differences show up straight away: removed lines in red, added lines in green, and the exact words that changed highlighted inside each line.
Pick side by side for reading documents, or stacked (unified) for code. Long stretches that didn’t change are folded away so you can focus on the edits.
Options let you ignore spaces, capital letters, or line-ending differences — the last one is handy when comparing a file saved on Windows with one saved on a Mac.
Developers: copy the result as a standard unified diff, ready for a patch or a code review.
FAQ
Side by side or unified — what’s the difference?
Same changes, different layout. Side by side is easier for reading documents; unified is what code reviews and patches use.
Can I copy the result as a patch?
Yes. “Copy as unified diff” gives you standard diff text that git and most review tools accept.
Why did it say it couldn’t do a detailed comparison?
The two texts were too different to compare line by line quickly, so the changed part is shown as one block. It’s still accurate, just less detailed.
What does the AI explanation do?
It sums up what changed in plain English, using a model built into your browser where available. It’s optional — the comparison works without it.
Can anyone else see my text?
No. Everything is compared on your device and nothing is sent anywhere.
How it worksFor the curious
The comparison uses Myers’ diff algorithm — the one git uses — which finds the shortest sequence of insertions and deletions turning one text into the other, so a changed word shows up as exactly that.
Each removed line is then paired with the line that replaced it and the two are diffed again by word. Pairing is positional within a change block on purpose: scoring lines for similarity starts inventing pairings that were never edits of one another.
Myers costs time proportional to the number of differences, so two entirely unrelated documents of several thousand lines could freeze the tab. Past that point the changed section is shown as a whole-block replacement, and the tool says so.
The optional AI explanation uses a language model built into your browser, on your device, where one exists. It receives only the changed lines, never both documents in full.