The Caesar cipher is one of the oldest known encryption methods, named after Julius Caesar, who used it to protect military messages. It works by shifting every letter a fixed number of places down the alphabet, so with a shift of three, A becomes D and Z wraps around to C. This tool lets you pick any shift from one to twenty five, encrypt your text, and decrypt it by applying the opposite shift. It is a classic teaching example of how substitution ciphers work and a fun way to pass simple coded notes, though it offers no real security by modern standards. Letter case is kept and non letters are untouched. Everything happens locally in your browser, so your messages stay private.