Text Diff Checker

This tool compares two blocks of text and shows you exactly what changed between them, line by line, marking what was added, removed or left unchanged. Comparing two versions of something is a constant need: checking what changed between two drafts of a document, two versions of a configuration file, two snippets of code, or two lists. Spotting the differences by eye is slow and unreliable, especially when the texts are long or the changes are small, and that is precisely what a diff tool is for. This checker lines up the two texts and works out the smallest set of changes that turns the first into the second, using the same kind of longest-common-subsequence approach that powers the diff tools developers rely on. You paste the original text into one box and the changed text into the other, and the calculator produces a combined view where unchanged lines are shown plainly, removed lines are marked with a minus, and added lines are marked with a plus. It also counts how many lines were added, removed and left unchanged, for a quick summary. The result updates as you edit, so you can compare and adjust on the fly. Everything runs in your browser, so your text stays private. Use it to review edits to a document, to see what changed in a file, to compare two lists, or to check code changes. The comparison works at the line level, which suits most documents, configuration and code. For the clearest results, keep each logical item on its own line, so that a single changed item shows as one removed and one added line rather than rearranging everything around it.

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Compares line by line using a longest-common-subsequence diff. Keep each logical item on its own line for the clearest results. Runs in your browser.