Caesar Cipher
Shift letters to encode or decode a Caesar cipher, with any shift from 1 to 25 including ROT13.
How to use it
- Enter your text The message to encode or decode.
- Set the shift Any number from 1 to 25 (13 is ROT13).
- Choose encode or decode Then copy the transformed text.
Examples
| abc, shift 3 | def |
|---|---|
| xyz, shift 3 | abc |
About this tool
The Caesar cipher is a classic introduction to cryptography: shift every letter a fixed number of places through the alphabet and the message becomes unreadable at a glance. This tool encodes and decodes with any shift, preserving capitalisation and leaving punctuation untouched.
It’s perfect for puzzles, classroom demos and the well-known ROT13 transformation. Remember it offers no real security — it’s for fun and learning, not protecting secrets. Everything runs in your browser.
Frequently asked questions
What is the Caesar cipher?
It's one of the oldest known ciphers — each letter is shifted a fixed number of places along the alphabet. Decoding simply shifts back by the same amount.
What about ROT13?
ROT13 is a Caesar cipher with a shift of 13. Because the alphabet has 26 letters, applying it twice returns the original text.
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Updated June 13, 2026