ROT13 & Caesar Cipher Tool
Encode and decode classical Caesar shift ciphers with custom shifts (1-25) and one-click standard ROT13 rotation.
1 How to Use the ROT13 & Caesar Cipher Tool
Type or paste your text into the message box.
Use the shift slider to choose any shift between 1 and 25 (default 13 for ROT13).
Or click the 'ROT13 Preset' button for instant symmetric rotation.
The cipher preserves upper and lower case letters while keeping numbers and punctuation unchanged.
2 Technical Specifications
| Specification | Details & Capabilities |
|---|---|
| Algorithm | Modular shift substitution cipher: C = (P + k) mod 26 |
| Shift Range | 1 to 25 positions |
| ROT13 Property | Self-inverse: applying ROT13 twice restores original text |
| Preservation | Preserves case, punctuation, spaces, and numbers |
Trust and Privacy
100% Client-Side Privacy Guarantee
All calculations run directly in your local browser memory. Zero data is ever transmitted, logged, or stored on remote servers.
4 Frequently Asked Questions
Q. What is the historical Caesar Cipher?
Named after Julius Caesar, who used a shift of 3 to protect military communications. It is the most famous classical substitution cipher in history.
Q. Why is ROT13 still used on online forums?
ROT13 is widely used on Reddit, Usenet, and puzzle forums to obscure spoilers, movie endings, and puzzle solutions without acting as heavy encryption.