What is the Caesar cipher?
The Caesar cipher shifts each letter of the alphabet by a fixed number of places. Shift the result back by the same amount to decode it. It's named after Julius Caesar, who reportedly used a shift of 3. ROT13 is simply a Caesar cipher with a shift of 13 — applying it twice returns the original text.
Example
With a shift of 3, HELLO becomes KHOOR. With ROT13, Hello becomes Uryyb.
Common uses of ROT13
- Hiding spoilers or puzzle answers in plain sight online.
- Teaching the basics of substitution ciphers.
Not for security: The Caesar cipher is trivial to break (there are only 25 possible shifts). Use it for fun and learning only — never to protect real data. For that, see our encryption and hashing tools.