Diff checker

Finding what changed

Comparing two versions of a contract, a config file, an API response or a translation by eye is slow and unreliable. A diff lists exactly which lines were removed, added or kept, in the minimum number of edits. This page uses the same algorithm as Git and GNU diff and shows the result in the familiar unified format: - for lines only in the original, + for lines only in the new version.

Ignore whitespace hides changes that are only spacing or trailing spaces, typical after reformatting. Ignore case hides capitalisation changes. Context sets how many unchanged lines appear around each change.

Worked example

Original: apples, bananas, cherries. Changed: apples, blueberries, cherries, dates. The diff shows apples unchanged, - bananas, + blueberries, cherries unchanged and + dates: 2 added, 1 removed, 2 unchanged.

Privacy

Many online diff tools upload both texts. Here the comparison runs in your browser, so you can compare confidential documents safely.

The page splits both texts into lines (treating Windows and Unix line endings alike), optionally normalises whitespace and letter case, and runs Myers' O(ND) diff algorithm, which finds the shortest sequence of line insertions and deletions that turns the first text into the second. The result is printed in unified style with the number of context lines you choose around each change, and long unchanged stretches collapse to …. Counts of added, removed and unchanged lines summarise the comparison. Everything runs in this tab; neither text is uploaded.