Diff Checker

Paste your original text on the left and the changed version on the right. The tool splits both into lines and finds the longest common subsequence — the lines that are unchanged — then marks everything else as added or removed. The result is a unified view with green additions, red deletions and running counts.

Yes. The diff is line-based, so it works equally well for source code, config files, JSON, Markdown or plain writing. For code where indentation changed but logic didn’t, turn on “Ignore whitespace” to focus on the real changes.

Ignore whitespace collapses runs of spaces and trims each line before comparing, so reflowed or re-indented lines aren’t flagged as different. Ignore case treats “Hello” and “hello” as the same line. Both change only how lines are matched — the text shown is always your original.

The tool compares up to 5,000 lines per side. Beyond that it shows a notice rather than the diff, because a line-level longest-common-subsequence comparison grows with the product of the two lengths and would get slow. For most documents and files you’ll never hit it.

No. Both blocks of text stay in your browser — the entire comparison runs locally, so you can safely diff private code or unpublished content.