Compare two blocks of text and see exactly what changed — free, no sign-up, nothing leaves your browser.
Rather than treating a change as one big block of "everything's different," a diff algorithm looks for the longest sequence of lines that appears unchanged in both versions, in the same order — then treats everything else around that shared backbone as either removed from the original or added in the new version. This is why moving a paragraph, rather than editing it, often shows up as a clean delete-and-reinsert instead of a wall of unrelated changes: the algorithm is finding the smallest set of edits that explains the difference between the two texts, not just marking every line that doesn't match its exact counterpart in the other version. It's the same underlying idea behind tools like git diff, applied here to any two blocks of text — contract revisions, config file changes, or two drafts of the same document.
Line by line — matching lines are shown as unchanged, removed lines are highlighted in red, and added lines are highlighted in teal, similar to a code diff view.
Very large texts (thousands of lines on each side) can be slow to compare since the algorithm's cost grows with the size of both texts multiplied together — there's a limit in place to keep the page responsive.
Whole lines — if a single character changes anywhere in a line, that entire line is shown as removed and its replacement shown as added, rather than highlighting just the changed word or character.
Yes — a line with different leading spaces, tabs, or trailing whitespace is treated as a different line from an otherwise-identical one, even though it might look the same on screen.
No. The comparison runs entirely locally in your browser — nothing you enter is sent to a server.