Caesar Cipher: The Classic Letter Shift, Explained and Tryable
The Caesar cipher is the oldest trick in the book for a reason: one shift rule scrambles a whole message, and the same rule unscrambles it.
What is the Caesar Cipher Tool?
A Caesar cipher moves every letter forward or backward through the alphabet by a fixed shift, wrapping from Z back to A. This tool handles upper and lower case separately and leaves spaces, digits, and punctuation untouched, so the shape of a sentence stays readable. Pick encode to scramble a message or decode to undo a shift you already know.
How to use it
- Type the message to encode or decode.
- Enter a shift from 0 to 25.
- Choose encode or decode.
- Click Apply Shift and copy the result.
Worked example
With shift 3, HELLO encodes to KHOOR.
How does a Caesar cipher shift letters?
Every letter moves the same number of steps through the alphabet, wrapping at the end. Decoding moves the same number of steps back.
Frequently asked questions
What shift turns HELLO into KHOOR?
A shift of 3 in encode mode: H becomes K, E becomes H, and so on through the word.
Is a Caesar cipher secure?
No. With only 26 possible shifts it is a puzzle and a teaching aid, not real encryption.