ROT13 Encoder / Decoder
Encode or decode text with the classic ROT13 cipher.
How to use the ROT13 Encoder / Decoder
- Type or paste your text.
- The ROT13 result appears instantly — run it again to decode.
About the ROT13 Encoder / Decoder
ROT13 replaces each letter with the one thirteen places further along the alphabet: A becomes N, B becomes O, and N wraps back around to A. Because 13 is exactly half of 26, the operation is its own inverse — applying it to already-rotated text returns the original. That is the whole charm of it: one tool, no separate encode and decode modes, and no way to get it the wrong way round.
It comes from Usenet, where it was the convention for posting anything a reader might not want to see immediately — a joke’s punchline, a plot spoiler, the answer to a puzzle. The point was never to stop someone reading it, only to stop them reading it by accident. Newsreader software had a key that rotated the text on the spot, so the barrier was exactly one keystroke high, and deliberately so. It is a politeness convention wearing the costume of a cipher.
Treat that as a hard rule: ROT13 provides zero security. It has no key, so there is no secret to protect — anyone who recognises it, and it is instantly recognisable, can undo it. Never use it for anything that matters. Only the 26 Latin letters are rotated here; digits, punctuation, spaces, accented letters and non-Latin characters all pass through untouched, and the case of each letter is preserved. Everything runs in your browser. For encoding that is meant to survive transport rather than to hide anything, see Base64; for genuine one-way hashing, the SHA-256 generator.
Frequently asked questions
Is ROT13 secure?
No. It offers zero security. There is no key, the method is universally known, and anyone can reverse it instantly. It exists to stop people reading something accidentally, not to stop them reading it deliberately.
How do I decode ROT13?
Run it through this tool again. Because the alphabet has 26 letters and ROT13 shifts by exactly half of that, applying it twice returns the original text. Encoding and decoding are the same operation.
What happens to numbers and punctuation?
They pass through unchanged. Only the letters A-Z and a-z are rotated. Digits, spaces, punctuation, accented letters and non-Latin characters appear in the output exactly as you typed them.
Does it preserve uppercase and lowercase?
Yes. An uppercase letter stays uppercase and a lowercase letter stays lowercase — only the letter itself changes, so "Hello" becomes "Uryyb".
What was ROT13 actually used for?
It was a Usenet convention for hiding spoilers, punchlines and puzzle answers from casual view. Readers who wanted to see the text pressed a key to rotate it; everyone else simply scrolled past. That remains its only sensible use.