🏛️ Caesar cipher

Shift every letter of the alphabet — from classic ROT13 to Julius Caesar's own cipher.

Shift3

The result appears here in real time

Turn this message into a real game: create a virtual lock your players must crack open.

The Caesar cipher shifts every letter of the alphabet by the same number of places: with a shift of 3, A becomes D, B becomes E, and so on. It's the simplest cipher to understand — and one of the most satisfying to crack once you spot the pattern.

It's named after Julius Caesar, who used it over 2,000 years ago to send secret military orders to his generals, so that a captured messenger couldn't hand the enemy a readable message. Its most famous modern version is ROT13, a fixed shift of 13.

For a treasure hunt or a homemade escape room, it's the perfect starting point: kids grasp the mechanism in thirty seconds, but still have to think to decode each letter. Print the matching alphabet grid, hide it separately from the coded message, and let the hunt begin.

How to use it

Type your secret message into the input field.
Set the shift you want (1-25) — or switch on ROT13 with one click.
Copy the encoded text or print the full alphabet grid.
Hide the message and let your players work out the shift.

Example(Shift : 3)

Plain message

THE KEY IS HIDDEN

Coded message

WKH NHB LV KLGGHQ

Reference grid

Frequently asked questions

How do you decode a Caesar cipher without knowing the shift?

Just try all 25 possible shifts one by one — a brute-force attack a computer solves in a split second. That's exactly why the Caesar cipher is great for teaching kids to decode, but far too weak to protect a real secret.

What's the difference between the Caesar cipher and ROT13?

None in principle: ROT13 is simply a Caesar cipher with a fixed shift of 13. Its neat trick is that it's symmetric — applying ROT13 twice returns the original text, which makes it easy to remember and apply by hand.

Can you turn a Caesar cipher into a real digital lock?

Yes — on CrackAndReveal you create a virtual lock where the expected answer is the decoded word. Players type their answer online, and the lock opens automatically once they've cracked the message, perfect for a treasure hunt with no adult supervision needed.

Is the Caesar cipher still used outside of ancient history?

Yes — it still shows up in games, in Reddit posts (ROT13 hides spoilers), and in classrooms as the first step in teaching cryptography before moving on to sturdier ciphers like Vigenère.

More secret codes

🪞 Atbash cipher

The mirror cipher: A becomes Z, B becomes Y, and the whole alphabet flips.

🗝️ Vigenère cipher

A Caesar cipher with a secret keyword, once called unbreakable for 300 years.

〰️ Rail fence cipher

Your message zigzags across several rails, then gets read off line by line.

All secret code decoders →·Go further →

Now hide this message behind a lock

With CrackAndReveal, your coded message becomes a virtual lock to crack: players decipher your code, enter the solution and reveal your surprise.

Create a free lock