ROT13 is a simple letter substitution that rotates each letter thirteen places through the alphabet, so A becomes N, B becomes O, and so on. Because the alphabet has twenty six letters, applying ROT13 twice returns the original text, which means the same button both scrambles and unscrambles. It is not real encryption and offers no security, but it has a long history online as a lightweight way to hide spoilers, punchlines, and puzzle answers so a reader has to opt in before seeing them. Numbers, spaces and punctuation pass through unchanged, and letter case is preserved. Type or paste your text and the transformed version appears instantly. Everything runs in your browser, so nothing is transmitted or logged anywhere.