Julius Caesar is said to have written to his generals with each letter moved three places along the alphabet, so A became D. It's the oldest cipher most people meet, and still the standard first exercise in cryptography classes and puzzle hunts.
Pick a shift and type. A shift of 13 is ROT13, the internet's way of hiding spoilers and punchlines, where encoding twice gets you back to the start. If you have a coded message and no key, list all 25 shifts and read down until one makes sense.
How to use the Caesar Cipher tool
- Type or paste the text.
- Set the shift, or tick decode.
- Copy the result, or list all shifts to crack a message.
Popular uses
- Puzzle hunts, escape rooms and geocaching clues
- Hiding spoilers with ROT13
- Teaching how ciphers and frequency analysis work
Tips for the best result
- Shift 13 for ROT13. The same setting encodes and decodes.
- Only A to Z are shifted. Accented letters, digits and punctuation pass through.
Quick facts
| Price | Free |
|---|---|
| Works with | Text |
| Where it runs | In your browser, on your device |
| Account | Not needed |