Caesar Cipher Decoder and Encoder
Shift every letter of your message along the alphabet to write a secret note, or decode one, even when you don’t know the shift.
Your cipher alphabet
| Plain | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cipher | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C |
Crack it: try every shift
Don’t know the shift? Here is the message decoded with all 25 shifts. Spot the one that makes sense and tap it.
Type a coded message above to see every possible answer.
How the Caesar cipher works
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Pick a number from 1 to 25. That is your shift, or key.
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Move each letter that many places along the alphabet. With a shift of 3, A becomes D, B becomes E and Z wraps around to C.
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To decode, move each letter back by the same number. Spaces, numbers and punctuation stay as they are.
Use the Caesar cipher in your own escape room
A Caesar cipher is perfect for escape rooms: hide the shift number somewhere in the room, like on a clock or a book page, and let players work out the message. Our printable escape rooms are full of puzzles like this, ready to print and play at home tonight.
Browse printable escape roomsCaesar cipher questions
What is the Caesar cipher?
The Caesar cipher is one of the oldest and simplest ciphers. Each letter is replaced by the letter a fixed number of places further along the alphabet. It is named after Julius Caesar, who used a shift of 3 to protect his messages.
How do you decode a Caesar cipher without the key?
There are only 25 possible shifts, so you can simply try them all. The crack it list on this page does that for you: read down until one line turns into real words.
What is ROT13?
ROT13 is a Caesar cipher with a shift of 13. Because the alphabet has 26 letters, using ROT13 twice brings you back to the original message, so the same step encodes and decodes.
Is this tool free?
Yes. It is free to use for puzzles, classrooms, games and secret messages, with no signup.
