Decode / Encode ROT13
Instantly encrypt or decrypt text with ROT13 — handy for reading a "spoiler" message found on a forum, solving a puzzle, or checking an exercise.
How it works
ROT13 ("rotate by 13 places") shifts each letter of the alphabet by 13 positions: A becomes N, B becomes O, and so on, preserving upper/lower case and leaving digits and punctuation unchanged. It's a classic on forums and online puzzles for hiding an answer, a joke or a spoiler without actually encrypting it: just paste the encoded text here to read it in plain text immediately.
Why is one single field enough to encode and decode?
Because the alphabet has 26 letters and the shift is 13, applying ROT13 a second time exactly cancels the first shift and recovers the original text. ROT13 is therefore its own inverse function: the same operation both encodes and decodes, and the conversion updates automatically as you type.
Does ROT13 really protect a text?
No, absolutely not. ROT13 isn't a security algorithm: there's no key and the shift is always the same, which makes it trivial for anyone to crack instantly. It's only meant to prevent a text (spoiler, puzzle answer) from being read by accident at first glance, not to protect sensitive information.
Conversion runs entirely in your browser via WebAssembly — the text entered is never sent to a server.