How it works
The two texts are compared line by line. Lines that are in both are shown as they are, lines only in the first are marked as removed with a minus, and lines only in the second are marked as added with a plus.
It finds the longest run of lines that both texts share, so a line that merely moved is shown as removed in one place and added in the other.
A line counts as changed if even one character differs, including spaces at the end of the line.
Good to know
Very long texts are not compared, to keep the page quick. Try a smaller piece.
Added and removed lines are marked with symbols as well as colour, so the result is clear without relying on colour.
Frequently asked questions
Does it show changes inside a line?
No. It compares whole lines. A line with a small change shows as one removed and one added.
Is my text sent anywhere?
No. Everything is compared in your browser.
Can it compare files?
Not directly. Open the file, copy the text and paste it in.