Text Diff

Two versions of a contract, a config file, an article, or a code snippet — and no idea what actually changed between them? Reading both side by side and hunting for differences by eye is slow, and it is painfully easy to miss a single edited line.

This tool compares two texts line by line and shows the result side by side: the original on the left, the changed text on the right. Removed lines are highlighted in red, added lines in green, and inside each edited pair the changed fragment is marked character by character. Everything happens in your browser — neither text is ever uploaded to a server, so private documents stay private.

The comparison is powered by the longest common subsequence algorithm, the same idea behind classic developer diff tools, so it finds the minimal set of changes instead of flagging everything after the first edit. Optional modes let you ignore letter case and collapse extra whitespace, which is handy when one version was reformatted or retyped.

Paste the original text on the left, the changed text on the right, and press Execute. You get an instant summary of how many lines were added and removed, a line-aligned side-by-side view just like in an IDE diff tool, and a one-click copy of the classic unified diff with "+" and "-" markers.