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Paste the original on the left and the changed version on the right: removed lines show red, added lines green, with line numbers and a change count. The comparison uses the longest-common-subsequence algorithm — the same family git diff uses — computed locally. Contracts, configs and code stay on your device.
Frequently asked questions
Why does the diff mark a line as changed when only one word differs?
This is a line-level diff: any difference within a line marks the whole line as removed-then-added. That granularity suits code and configs; for prose, comparing sentence-per-line input gives more readable results.
Does whitespace count as a difference?
Yes — trailing spaces, tabs-vs-spaces and blank lines are real changes, exactly as git sees them. Invisible differences are a classic source of "identical" texts that don't match.
How large a text can I compare?
Unchanged beginnings and endings are skipped instantly, so even long documents diff fast when the changes are localised. Only pathological cases (thousands of differing lines on both sides) hit the size guard.