ROT13 is one of the simplest ciphers ever devised: it rotates each letter 13 places through the alphabet. Because the English alphabet has 26 letters, applying ROT13 twice returns the original text — encoding and decoding are the same operation.
How it works
A becomes N, B becomes O, and so on. Numbers and punctuation are left untouched. It offers no real security, so it is never used to protect secrets; instead it hides text from casual view.
Where ROT13 is used
For decades it has hidden spoilers, punchlines and puzzle answers in online forums, so readers must deliberately decode them. It is also a popular teaching example for how substitution ciphers work.
Encode and decode instantly
Paste your text and apply ROT13 to scramble or reveal it. Everything happens locally in your browser, so it is quick and private — perfect for hiding a spoiler or solving one.