Caesar Cipher Tool

Encode and decode a Caesar cipher

The Caesar cipher shifts every letter a fixed number of places along the alphabet, the technique attributed to Julius Caesar for his private messages. Set the shift, type your text, and the result updates as you go; to decode, use the matching shift in the opposite direction or its complement. ROT13 is just this cipher with a shift of thirteen. Letters wrap around from Z back to A, while digits and punctuation are left alone. The cipher runs entirely on your device.

Choosing a shift

Any value from 1 to 25 works. To undo a shift of n, apply a shift of 26 minus n, which brings the text back to the start.