Caesar Cipher
Shift letters by a custom offset using the classic Caesar substitution cipher.
Named after Julius Caesar, who used it with a shift of 3 to protect military dispatches. To decrypt, simply rotate in the opposite direction (e.g. shift of 26 minus the original key).
What is Caesar Cipher?
This Caesar cipher tool shifts every letter in your text by a fixed number of positions in the alphabet to encode or decode messages. It's the classic cipher taught in introductory cryptography and computer science courses, and works as both a caesar cipher encoder and caesar cipher decoder. Adjust the shift value to encode text or try all 25 possible shifts to crack an unknown Caesar-encoded message.
How It Works
The tool takes each letter in your input and shifts it forward (or backward, for decoding) through the alphabet by the number of positions you specify, wrapping around from Z back to A as needed; non-letter characters like spaces and punctuation are left unchanged. Because there are only 26 possible shifts, Caesar ciphers are trivially breakable by brute force, which is why they're used for education rather than real security.
Is It Safe to Use?
All shifting happens locally in your browser's JavaScript; your text is never uploaded to a server, so classroom exercises or private notes stay on your device.
How to Use Caesar Cipher (Step-by-Step Guide)
- Enter the text you want to encode or decode.
- Set the shift value (how many letters to move, 1-25).
- Choose encode or decode mode.
- The tool instantly shifts every letter accordingly.
- Copy the result, or try different shift values to decode unknown ciphertext.