What is ROT13?
ROT13 ("rotate by 13 places") is a simple substitution cipher that replaces a letter with the 13th letter after it in the alphabet. It is a special case of the Caesar cipher.
Because there are 26 letters in the basic Latin alphabet, ROT13 is its own inverse; that is, to reverse ROT13, the same algorithm is applied, so the same action can be used for encoding and decoding. The algorithm provides virtually no cryptographic security, and is often cited as a canonical example of weak encryption.
Common Uses
ROT13 is frequently used in online forums as a means of hiding spoilers, punchlines, puzzle solutions, and offensive materials from the casual glance. It is also a popular coding exercise for beginners.