Puzzle tools
Caesar cipher
Pick a shift and type your message: the result updates as you type. Don’t know the shift? Show all 25 possibilities and spot the one that makes sense.
How does the Caesar cipher work?
Every letter of the message is replaced by the letter a fixed number of places further down the alphabet. With a shift of 3, A becomes D, B becomes E, and so on. After Z it wraps around: X becomes A, Y becomes B, Z becomes C.
To decode, go the other way: move each letter back by the same number of places. Spaces, digits and punctuation stay as they are.
Example
With a shift of 3, “MEET AT MIDNIGHT” becomes “PHHW DW PLGQLJKW”. To read it, move every letter back 3 places.
Where does it come from?
According to the historian Suetonius, Julius Caesar used it with a shift of 3 for his military letters. It is one of the oldest known ciphers, and one of the easiest to break: there are only 25 possible shifts, and you can try them all in seconds.
Using it in an escape game
The Caesar cipher makes a perfect first puzzle: players recognise it quickly, and the shift can be hidden elsewhere (the time on a clock, the candles on a cake, a date). The better the shift is hidden, the more satisfying the puzzle.
A well-known variant is ROT13, a Caesar cipher with a shift of 13. It has a neat property: applying it twice gives back the original text.
Reference table
ABCDEFGHIJKLMNOPQRSTUVWXYZ → DEFGHIJKLMNOPQRSTUVWXYZABC (+3)
Frequently asked questions
How do I decode a Caesar cipher without knowing the shift?
Click “Try all 25 shifts”: the tool shows the message shifted by 1 to 25 places. Only one line forms readable words, and that’s the solution.
What happens to accented letters?
Accented letters are turned into their base letter (é becomes e) before shifting, just as you would on paper with a 26-letter alphabet.
How is it different from the Vigenère cipher?
Caesar shifts every letter by the same amount. Vigenère changes the shift at every letter, following a keyword, which makes it much harder to break.
Turn your message into a puzzle
On In-Evasion you build a free online escape game: every puzzle has its code, each code found opens the next one, and your players solve it all together on a shared board.