This tool applies a Caesar cipher: each letter is shifted a fixed number of positions along the alphabet, so with a key of 3 the word 'hello' becomes 'khoor'. Decryption simply shifts back by the same amount, and shifting by 13 gives you ROT13, where a single operation both encodes and decodes. Digits, punctuation and spaces pass through untouched, and letter case is preserved. The Caesar cipher is roughly 2,000 years old and has only 25 usable keys, so it is trivially broken by trying every shift — treat it as a teaching aid, a puzzle generator or a light spoiler-hiding trick, never as real protection for sensitive information.
Free, fast, and runs entirely in your browser — no signup, no upload to a server.