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The Caesar cipher is one of the oldest known encryption techniques, shifting every letter of a message a fixed number of positions through the alphabet.
This tool encrypts or decrypts text using a Caesar cipher with a shift amount you choose.
How it works
Enter your text and a shift amount from 1 to 25. Each letter moves forward (to encrypt) or backward (to decrypt) that many positions in the alphabet, wrapping around from Z back to A. Non-letter characters are left unchanged.
- Enter mode.
- Enter text.
- Enter shift (1-25).
- Click Calculate to see your results.
Examples
Shift of 3
"Attack at dawn" encrypted with a shift of 3 becomes "Dwwdfn dw gdzq".
Who should use it
- Puzzle and escape-room style word games.
- Teaching the basics of substitution ciphers and cryptanalysis.
Industry applications
- Cryptography education
- Games and puzzles
Advantages
- Simple, fast, and easy to understand and verify by hand.
- A good first introduction to substitution ciphers.
Limitations
- Trivially breakable — only 25 possible shifts to try.
Common mistakes to avoid
- Using the same shift for encryption and decryption without accounting for direction — decrypting requires shifting backward by the same amount used to encrypt.
- Assuming a Caesar cipher provides real security for sensitive information.
Best practices
- Use the Caesar cipher for puzzles, games, or teaching cryptography concepts — not for protecting anything sensitive.
Tips
- If you don't know the shift used to encrypt a message, try all 25 possible shifts — this is called a brute-force attack, and it's exactly why the Caesar cipher isn't secure.