How to compare two texts and see what changed
A revised contract next to the original, two copies of a config file, the same email answered twice — when two blocks of text are nearly identical, reading them side by side almost guarantees you will miss a line. Paste one into A and the other into B, press compare, and removed lines show in red while added lines show in green.
The comparison uses a line-based longest common subsequence. Rather than lining up row one against row one, it first finds the longest run of shared lines, so inserting a single line near the top does not make everything below it look rewritten. The work grows with the square of the line count, so each side is limited to 2,000 lines per run.
Two options let you ignore letter case and whitespace differences. With whitespace ignored, lines that differ only in indentation or trailing blanks count as identical. Changes are reported per line, not per character: a line with a single edited word appears as one removal plus one addition. Anything you paste is escaped before it reaches the screen, so HTML or script tags are shown as literal text and never run. All of the work happens in your browser.
Frequently asked questions
No. This is a line-level comparison, so a line with one changed character is shown as a removed line and an added line next to each other.
Each text can hold up to 2,000 lines. The algorithm scales with the square of the line count, and anything larger returns a notice instead of a result.