How this text comparison works
The checker splits both texts into lines and finds their longest common subsequence — the biggest run of lines the two versions share in order. Lines outside that backbone are the actual changes: present only in the original means removed (−, red), present only in the changed text means added (+, green). This is the same principle behind git diff and the classic Unix diff tool, so the output reads like a patch you have seen a hundred times. The comparison runs entirely in your browser; nothing you paste is uploaded.
How to compare two texts
- Paste the original version on the left and the edited version on the right.
- Click Compare and scan the red/green lines and the added/removed counts.
- For prose, put one sentence per line first — reflowed paragraphs otherwise mark every line as changed.
Getting cleaner diffs
Diff noise almost always comes from formatting, not content. Watch for trailing whitespace and mixed line endings (a Windows \r\n file against a Unix \n file differs on every line), and normalize indentation before comparing code. A line edited in place appears as a remove-plus-add pair — that is standard diff behavior, not two separate changes. If you are comparing JSON, the JSON Diff tool understands structure and ignores key order and formatting entirely, which is usually what you actually want for API payloads.