How ROT13 works
ROT13, short for rotate by 13 places, replaces each letter with the one 13 places further along the alphabet: A becomes N, B becomes O, and N wraps round to A. The English alphabet has 26 letters, so shifting by 13 twice gets you back to the start. That means the same step both hides and reveals a message.
Type or paste your text and the result appears at once. Upper and lower case are kept, and numbers, spaces and punctuation are not changed.
What ROT13 is used for
ROT13 became popular on Usenet discussion groups in the early 1980s as a polite way to hide spoilers, puzzle answers and punchlines. Readers who wanted to see them could decode the text in one step, and everyone else could scroll past without reading by accident.
It is still used today for spoilers, puzzle solutions and hiding answers in quizzes. It is not a way to keep anything secret, because there is no key and anyone can undo it.
ROT13 is simply a Caesar cipher with a shift of 13. For other shifts, use the Caesar cipher tool, which can also crack a shift you do not know.
A handy way to check you have ROT13 right: the first half of the alphabet, A to M, swaps with the second half, N to Z. So A and N swap, B and O swap, and M and Z swap.
Questions and answers
How do I decode ROT13?
Paste the text into the box. ROT13 decodes the same way it encodes, so the readable text appears straight away.
Does ROT13 change numbers?
No. Only letters change. A related scheme called ROT47 also shifts numbers and symbols, but it is less common.
Is ROT13 encryption?
Not in any useful sense. It hides text from a casual glance but offers no security at all.
What is ROT13 of HELLO?
URYYB.