Caesar Cipher & ROT13

Encode and decode the Caesar cipher with any shift, ROT13, or brute-force all 25 shifts.

How does the Caesar cipher work?

The Caesar cipher replaces each letter with the letter a fixed number of places later in the alphabet. With a shift of 3, A becomes D and “HELLO” becomes “KHOOR”. ROT13 is the special case with shift 13, which decodes itself when applied twice.

Modes

Encode / Decode with any shift from 1 to 25.
ROT13 — common for hiding spoilers and puzzle answers.
Brute force lists all 25 possible shifts so you can spot the readable one.

Only letters are shifted; numbers, spaces and punctuation stay the same, and upper/lower case is kept.

Frequently asked questions

Is the Caesar cipher secure?

No — there are only 25 keys. Use it for puzzles and teaching, not for secrets.

Why is it called Caesar?

Julius Caesar reportedly used a shift of 3 for military messages.

Does it support other alphabets?

It shifts the 26 Latin letters A–Z.