How to Use Caesar Cipher / ROT13
Shift letters by any amount to encode or decode a classic Caesar cipher, with a one-click ROT13 preset.
Open the Caesar Cipher / ROT13 tool →What is Caesar Cipher / ROT13?
Encode and decode text with a Caesar shift cipher (including ROT13). It's completely free, needs no sign-up, and runs entirely in your browser — so it's fast and private.
How to use Caesar Cipher / ROT13
- Open the Caesar Cipher / ROT13 tool.
- Paste or type your input.
- Set any options provided.
- Copy the result. Everything runs in your browser — nothing is uploaded.
Frequently asked questions
What is a Caesar cipher?
A simple substitution cipher that shifts each letter a fixed number of places in the alphabet. ROT13 is the special case with a shift of 13.
Is it secure?
No — it's a classic puzzle cipher and is trivially broken. Never use it to protect real secrets.
Why is ROT13 self-reversing?
Because the alphabet has 26 letters, shifting by 13 twice returns the original, so the same operation both encodes and decodes.
Ready to try it?
Open Caesar Cipher / ROT13 →