Caesar Cipher Encoder & Decoder
Encrypt or decrypt text with the classic Caesar shift cipher (any shift -25 to 25).
Shift each letter by a fixed number of places — the simplest substitution cipher, named after Julius Caesar's military despatches. Adjust the shift with a slider, toggle decode mode, and the cipher preserves case while passing punctuation through.
Common use cases
- Encode short notes for kids' spy games or party clues
- Demonstrate substitution ciphers and modular arithmetic in class
- Solve cryptic Caesar puzzles in escape rooms and CTFs
- Quickly try all 25 shifts to brute-force-decode an unknown ciphertext
Frequently asked questions
Is the Caesar cipher secure?▾
No — there are only 25 possible shifts, so it's trivially brute-forced. It's a teaching tool and party-game cipher only.
What shift should I use?▾
The classic Caesar uses shift 3. ROT13 is shift 13. Any value -25 to 25 works; positive shifts encode forward, negative shifts decode.
Why preserve case?▾
It keeps the ciphertext readable and lets you decode 'Hello' back to 'Hello' without losing capital letters.
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