Caesar Cipher.

The foundation of cryptography. Rotating the alphabet by a fixed offset to hide your words.

Rotation Offset

Original Text

Ciphered Result

...

Historical Background

Named after Julius Caesar, who used it to protect military correspondence around 50 BC. With only 25 possible shifts, it can be brute-forced in seconds — making it a perfect teaching tool for understanding substitution ciphers, but entirely unsuitable for real security. ROT13 (shift 13) is a well-known special case still used for spoiler text.