ROT13 Cipher

About this calculator

This tool applies ROT13, a simple substitution cipher that shifts every letter 13 positions through the alphabet, wrapping from Z back to A. Because the alphabet has 26 letters, applying the same 13-position shift a second time reverses the first, which is why the identical operation both encodes and decodes any message — there's no separate decrypt step or key to manage.

ROT13 provides no real security since it is trivial to break, so it was never intended to protect sensitive information; instead it is traditionally used on forums and newsgroups to obscure spoilers, puzzle answers, or offensive jokes from someone's screen so readers have to actively choose to decode the text before seeing it. Programmers also use it informally as a lightweight obfuscation for test data, throwaway examples, or hiding an answer key in a document where casual glancing shouldn't reveal it immediately.