Caesar Cipher
Encode and decode text with a shift cipher, including ROT13.
Caesar Cipher Encoder & Decoder
The Caesar cipher shifts each letter of the alphabet a fixed number of places. Choose a shift, pick encode or decode, and the tool transforms your text instantly. A shift of 13 produces the well-known ROT13 cipher.
How it works
- Each letter moves N places along the alphabet
- Wraps around from Z back to A
- Numbers, spaces, and punctuation stay unchanged
- Decoding simply shifts in the opposite direction
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 operation both encodes and decodes.
A piece of cryptography history
Named after Julius Caesar, who reportedly used it to protect military messages, the Caesar cipher is one of the oldest known encryption techniques. It is trivial to break today but remains a perfect introduction to how substitution ciphers work.
100% Private & Processed Locally
All encoding and decoding happens in your browser. Your text is never uploaded.
Frequently Asked Questions
Common questions about the Caesar Cipher.