A text diff checker for seeing exactly what changed between a "before" and an "after" version of any text. Paste the original on the left and the changed text on the right, and it matches them with the LCS (longest common subsequence) algorithm, highlighting removed parts in red and added parts in green. You can compare at three granularities: line, word, or character. Line mode shows additions and deletions per line with `+`/`-` gutters like a Git diff, ideal for config files and code. Word mode reveals which words were swapped in prose, and character mode catches single-character typos and subtle differences down to one glyph. Turn on "Ignore case" to treat `Hello` and `hello` as the same, and "Ignore whitespace" to disregard indentation, extra spaces, and line-ending differences so you compare just the content. Counts of additions and deletions appear at the top so you can gauge the size of the change at a glance, and a "Swap" button flips the two sides entirely. Your chosen granularity and ignore options are saved in your browser so the next visit starts with the same settings (the pasted text itself is not stored). Importantly, the text you enter is never uploaded, stored, or sent to a server — all computation happens with JavaScript entirely inside your browser, so contract revisions, unreleased drafts, and internal documents you can't share stay on your device. Note that this tool focuses on plain-text diffing: it does not read formatted files like Word or PDF directly, compare three or more versions at once, or export a patch (unified-diff) file.