ROT13 / Caesar Cipher
Encrypt and decrypt text with the Caesar cipher or ROT13.
Cipher alphabet mapping
About this tool
Processing happens directly in your browser. No files are uploaded to the server.
Caesar Cipher shifts each letter in the text by a fixed number of positions. ROT13 is the special case with a shift of 13 (applying it twice gives back the original). Numbers and special characters are preserved unchanged.
How to use
- 1 Paste your text into the input box.
- 2 Adjust the shift slider or click the ROT13 preset button.
- 3 Choose Encrypt or Decrypt.
- 4 The result updates instantly. Copy the output.
Frequently asked questions
What is ROT13?
ROT13 rotates each letter by 13 positions. Because the alphabet has 26 letters, applying ROT13 twice restores the original text.
Does it work on numbers?
No. Only AβZ and aβz are shifted; digits and symbols stay unchanged.
Is Caesar cipher secure?
No. It is one of the oldest and easiest ciphers to break. Use it for fun or obfuscation only.
What shift should I use for Encrypt?
Any shift from 1 to 25. The receiver must know the same shift to decrypt.