Caesar Cipher

Free Caesar Cipher

Encrypt and decrypt messages using the classic Caesar shift cipher named after Julius Caesar. Pick any shift from 1 to 25, or use shift 13 for ROT13.

Common Uses

• Build escape-room and puzzle clues
• Teach cryptography fundamentals in class
• Decode classroom CTF challenges
• Send playful hidden messages to friends
• Demonstrate frequency analysis as a follow-up

How It Works

Each letter is shifted by the chosen amount within the 26-letter English alphabet. Non-letter characters are preserved exactly. Decryption uses the negative of the shift, with modular arithmetic to wrap around the alphabet.

Privacy

Everything runs locally. The text is never transmitted.

Related: ROT13 Encoder, Vigenere Cipher, Morse Code Translator.

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