TOOLEncode and decode with a shift cipher
The Caesar cipher shifts every letter along the alphabet by a fixed amount — one of the oldest and simplest ciphers there is. Set a shift to encode, use a negative shift (or the reverse button) to decode, or hit ROT13 for the classic shift-13 that encodes and decodes with the same action. Non-letters are left untouched.
Good to know
A Caesar cipher is fun for puzzles and hiding spoilers, but it offers no real security — it's trivial to break. For anything sensitive you need proper encryption. Learn how modern encoding differs in what is Base64 encoding, or try the Base64 tool.
Frequently asked questions
What is a Caesar cipher?
A Caesar cipher shifts every letter forward in the alphabet by a fixed amount. Shift by 3 and A becomes D, B becomes E, and so on, wrapping around from Z back to A.
What is ROT13?
ROT13 is a Caesar cipher with a shift of 13. Because the alphabet has 26 letters, applying ROT13 twice returns the original text, so the same action encodes and decodes.
Is a Caesar cipher secure?
No. It is a simple, easily broken cipher meant for puzzles, obscuring spoilers, or learning about cryptography — not for protecting sensitive information.