Caesar Cipher / ROT13
Encode or decode text with a Caesar cipher (including the classic ROT13 shift), with any shift amount from 1 to 25 — instantly, in your browser.
Shift each letter along the alphabet to encode or decode a Caesar cipher or ROT13. It runs in your browser.
How to use it
- Paste your text.
- Choose a shift (13, 1, 2, 3, 4, 5, 10, 20 or 25) and encode or decode.
- Copy or download the result.
Examples
- Shift 3: “Hello, World!” becomes “Khoor, Zruog!”.
- Shift 13 (ROT13): “Hello, World!” becomes “Uryyb, Jbeyq!”, and applying it again returns the original.
Good to know
Only letters change, and capitals stay capitals; digits, spaces and punctuation are untouched. The tool starts on 13 because ROT13 is the most common use. Suetonius records Caesar using a shift of 3. This is not security: there are only 25 shifts and letter frequencies give it away, so use it for puzzles, teaching or hiding a spoiler, never for anything private.
Read the guide or the glossary entry.
FAQs
Why does shift 13 decode itself?
The alphabet has 26 letters, so shifting by 13 twice returns every letter to where it began.
Does it handle accented letters?
It shifts the basic letters A to Z only; accented letters and other scripts are left unchanged.