Caesar Cipher Encoder Online

The Caesar Cipher is the "Hello World" of cryptography. Legend has it that Julius Caesar used it to encrypt military orders by simply shifting every letter in the alphabet by 3 spaces. Today, developers use it for fun coding challenges, geocaching puzzles, and hiding spoilers on forums. This tool is built to instantly shift text back and forth.

How the ASCII Math Works

The code looks at the numerical ASCII value of each letter you type. If you set a shift of 5, it adds 5 to that number and prints the new letter. The tricky part of writing a cipher is the "wrap-around." If you shift the letter 'Z' by 1, the script is smart enough to wrap back around to 'A' rather than printing a random punctuation mark.

The Magic of ROT13

If you select a shift of 13, you are using the famous ROT13 cipher. Because the English alphabet has 26 letters, shifting by exactly half means that the "Encode" and "Decode" buttons do the exact same thing. It is mathematically symmetrical.

An Important Warning

Do not use a Caesar Cipher to protect actual secrets like passwords or API keys. Because there are only 25 possible combinations in the English alphabet, a computer script can brute-force and crack a Caesar cipher in roughly two milliseconds.