How it compares
The two texts are compared line by line using the longest-common-subsequence algorithm — the same idea behind git diff. Removed lines are red with a −, added lines green with a +, and when a line was modified, the changed part inside it is highlighted more strongly. Line numbers show where each line sits in the original (left) and changed (right) text.
Both texts stay in your browser — nothing is uploaded and nothing is tracked. They are remembered only on this device.