Caesar Cipher
Shift letters to hide a message — or crack one when you don't know the key.
- Your data never leaves your device
- 100% free
- No sign-up
- Works offline after first load
How to encode or decode a Caesar cipher
- Type or paste the message.
- Choose the cipher, the direction and the shift or keyword.
- Copy the result — or crack an unknown shift.
About Caesar Cipher
Encode and decode the Caesar cipher with any shift.
It works in your browser for speed and privacy, remembers your settings on this device, and every result can be copied, downloaded or shared.
Good for
- Puzzles, escape rooms and geocaching
- Teaching cryptography
- Hiding spoilers
Tip: Long messages crack more reliably — the tool needs enough letters to compare frequencies.
Frequently asked questions
How does the Caesar cipher work?
Each letter is moved a fixed number of places along the alphabet: with a shift of 3, A becomes D and Z wraps round to C. Decoding moves the letters back.
Can it decode without the key?
Yes — choose “Crack”. All 25 shifts are tried and ranked by how closely their letter frequencies match English, so the right answer is usually first.
Which other ciphers are included?
Atbash (reverses the alphabet), Vigenère (a keyword gives each letter a different shift) and Affine (multiply and add).
Is the Caesar cipher secure?
No — it is for fun, puzzles and teaching. Use the Encrypt / Decrypt Text tool for real secrets.
Is my text uploaded?
No. Everything runs in your browser and nothing you type is sent anywhere.