Encode and decode text using ROT13 cipher. Also supports custom rotation values (ROT1-ROT25).
ROT13 (rotate by 13 places) is a simple letter substitution cipher that replaces each letter with the letter 13 positions after it in the alphabet. Since the English alphabet has 26 letters, applying ROT13 twice returns the original text — making it its own inverse. ROT13 is not encryption (it provides no real security), but it's commonly used to hide spoilers, puzzle answers, and offensive content in online forums. It's also a classic example in computer science for teaching about ciphers and character manipulation.
No. ROT13 is a trivial cipher with no key — anyone who knows about it can decode it instantly. Never use it for sensitive data. For real encryption, consider proper tools.
Because the alphabet has 26 letters, shifting by 13 twice brings you back to the start (13 + 13 = 26). This makes ROT13 uniquely self-reversing.
It's used on forums to hide spoilers, in online puzzle communities, and as a teaching example in programming and cryptography courses.
Standard ROT13 only transforms letters (A-Z, a-z). Numbers, spaces, and punctuation remain unchanged.
ROT5 rotates digits (0-9) by 5 places, and ROT47 rotates all ASCII printable characters. These are variations of the same concept.