ROT13 ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple substitution cipher used in online forums as a means of hiding spoilers, punchlines, puzzle solutions, and offensive materials from the casual glance. ROT13 has been described as the "Usenet equivalent of a magazine printing the answer to a quiz upside down". ROT13 is a variation of the Caesar cipher, developed in ancient Rome. ROT13 is its own inverse; that is, to undo ROT13, the same algorithm is applied, so the same actio… (More on Rot13)