Caesar Cipher

The classic shift cipher: every letter moves a fixed number of places through the alphabet. Adjust the shift to encode or decode.

How to use it

Shift, read, reverse.

Set a shift

Drag the slider to choose how many letters each character moves through the alphabet.

Type your message

The encoded version appears instantly on the right as you type.

Decode by reversing

To read an encoded message, paste it on the left and set the shift to 26 minus the original number.

Where this comes up

Common uses for the Caesar cipher.

Learning cryptography basics — it's the standard first example before moving to modern ciphers.
Puzzle hunts & escape rooms — a classic, easy-to-verify-by-hand obfuscation layer.
Light text obfuscation — hiding non-sensitive text from a casual glance (not secure encryption).
Programming exercises — a common “write a cipher” assignment in intro coding courses.

FAQ

Caesar cipher, explained.

Is the Caesar cipher secure?

No — with only 25 possible shifts, it can be brute-forced by hand in minutes. It’s included here for learning and puzzles only. For anything that actually needs to stay private, you need real encryption, not a classical cipher — and note that Base64 isn’t encryption either, just an encoding.

What's ROT13?

ROT13 is just a Caesar cipher with the shift fixed at 13. Set the slider on this page to 13 to get the same result — and since 26 ÷ 2 = 13, applying it twice always returns the original text.

How do people crack a Caesar cipher without knowing the shift?

Either by brute force (there are only 25 shifts to try) or by frequency analysis — in English, 'E' is the most common letter, so the most frequent symbol in the ciphertext is a strong hint at the shift used.

Does this handle numbers and punctuation?

No, the shift only applies to letters A–Z (preserving case) — numbers, spaces and punctuation pass through unchanged, matching how the classical cipher was originally defined.