What is the difference between a Caesar cipher and ROT13?

ROT13 is simply a Caesar cipher with a fixed shift of 13. This tool lets you pick any shift from 0 to 25, so a shift of 13 reproduces ROT13.

How do I decrypt a message?

Switch to Decrypt and enter the same shift that was used to encrypt. The tool rotates each letter back by that amount to recover the original text.

Is my message uploaded anywhere?

No. The cipher runs entirely in your browser with JavaScript, so your message never leaves your device.

Caesar Cipher

Encrypt and decrypt text with a shifting Caesar cipher.

Caesar cipher

The Caesar cipher shifts every letter a fixed number of places through the alphabet. Pick a shift from 0 to 25, choose encrypt or decrypt, and the result updates instantly. A shift of 13 is identical to ROT13.

Digits, spaces and punctuation are left unchanged. Everything runs in your browser — nothing you type is uploaded.