ROT13 / Caesar Cipher
Shift each letter by a fixed amount. ROT13 is just a Caesar cipher with a shift of 13.
Why ROT13 undoes itself
Since the alphabet has 26 letters, shifting by 13 twice returns every letter to where it started — so the same ROT13 button both encodes and decodes.
About the ROT13 / Caesar Cipher
This tool encodes and decodes text with ROT13 or any Caesar cipher shift. It is a fun way to learn about simple ciphers, solve puzzles and hide spoilers.
A Caesar cipher replaces each letter with the letter a fixed number of places further along the alphabet. ROT13 uses a shift of 13, and because the English alphabet has 26 letters, applying ROT13 twice returns the original text. These ciphers are not secure and can be broken in seconds, so never use them to protect real information.
How to use it
- Type or paste text.
- Press Apply ROT13, or set a shift and press Apply custom shift.
- Read the result.
- To decode a Caesar shift, apply the opposite shift (26 minus the shift).
Tips and good to know
- Numbers and punctuation are not changed.
- Case is preserved.
- Try all 25 shifts if you do not know the key.
Frequently asked questions
Is ROT13 encryption?
No, it is only obfuscation.
How do I decode a shift of 3?
Use a shift of 23, or apply a shift of −3.
Does it work with other alphabets?
It supports the English alphabet.