Cipher
ROT13 Decoder and Encoder
ROT13 rotates every letter 13 places through the alphabet. Because 13 is exactly half of 26, encoding and decoding are the same operation, so one button does both.
Result appears here
It is famous online for hiding spoilers and punchlines in plain sight. Type anything and the ROT13 version appears instantly, all in your browser.
How the ROT13 works
Each letter moves forward 13 positions, wrapping around the end of the alphabet. A becomes N, N becomes A, and so on. Numbers, spaces and punctuation are untouched.
Since the shift is 13 both ways, running ROT13 on ROT13 output returns the original text. That symmetry is why the same tool encodes and decodes.
Examples
History and origins
ROT13 grew up on early internet forums and Usenet in the 1980s as a light way to hide spoilers, answers and offensive jokes so readers had to opt in to see them.
It was never meant as encryption. It is a social convention, a gentleman's agreement that you will not read the hidden text unless you choose to decode it.
Frequently asked questions
How do I decode ROT13?
Run ROT13 on the encoded text again. Because the shift is half the alphabet, applying it a second time undoes it and reveals the original message.
Is ROT13 secure?
No. It offers zero security and is trivial to reverse. Its whole purpose is to hide text from casual view, such as a spoiler, not to keep secrets.
Learn more
Go deeper on the ideas behind this tool.