ROT13 Cipher

You want to post a puzzle solution, a movie ending or a hint without spoiling it for anyone who merely scrolls past. ROT13 does exactly that: every letter shifts 13 places down the alphabet, the text turns to gibberish at a glance, and anyone who actually wants to read it can decode it in seconds. Paste your text in the left box and the output updates live as you type.

The trick is in the number 13: the alphabet has 26 letters, so applying the shift twice brings the original back. That is why there is no decrypt mode; one operation does both jobs. Only the letters A to Z are changed. Digits, punctuation and accented letters pass through untouched, which leaks structure: in a word like 'café', three letters move but the é stays put, hinting at the original word.

Use it for forum spoilers, quiz answer keys and geocaching hints, where ROT13 has been the convention for decades; it goes back to Usenet in the early 1980s. Never use it for anything sensitive: with no key involved, anyone reverses it instantly. Everything runs in your browser, and nothing you type is sent to any server, so pasting a long text is fine.