Caesar Cipher Encoder & Decoder
Encode and decode the Caesar cipher with any shift from 1 to 25 — the classic letter-shifting cipher used since Roman times.
What is the Caesar cipher?
The Caesar cipher shifts every letter a fixed number of places along the alphabet. With a shift of three, A becomes D and B becomes E. It is named after Julius Caesar, who reportedly used it to protect military messages, and it is the classic starting point for learning about codes.
How to use this Caesar tool
- Choose Encode or Decode.
- Set the shift (1–25).
- Type your text and copy the result.
How the Caesar cipher works
Each letter moves the chosen number of positions through the alphabet, wrapping around from Z back to A. To decode, the same shift is applied in the opposite direction. If you do not know the shift of a message, you can try all 25 values until the text reads clearly — there are only 25 possibilities, which is why the Caesar cipher is easy to break.
Caesar vs. ROT13
ROT13 is just a Caesar cipher locked to a shift of 13. Because 13 is half of 26, encoding and decoding are the same operation. This tool lets you pick any shift you like.
More codes and ciphers
Explore the rest of the family: the Caesar Cipher, Atbash, Vigenère, and A1Z26. For other encodings, try the Morse Code Translator and the Binary Translator.
Free and private
This Caesar cipher tool runs entirely in your browser — free, with no sign-up, and nothing you type is uploaded or stored.
Frequently asked questions
- What is the Caesar cipher?
- The Caesar cipher shifts every letter a fixed number of places down the alphabet. With a shift of 3, A becomes D, B becomes E, and so on. It is named after Julius Caesar, who used it for military messages.
- How do I decode a Caesar cipher?
- Choose the Decode direction and enter the same shift used to encode it — the tool shifts each letter back. If you do not know the shift, try each value 1–25 until the text reads clearly.
- What is the difference between Caesar and ROT13?
- ROT13 is simply a Caesar cipher with a fixed shift of 13. Because 13 is half of 26, ROT13 is its own inverse. The Caesar tool lets you pick any shift from 1 to 25.
- Is it free and private?
- Yes — it runs entirely in your browser with no sign-up, and nothing you type is uploaded.
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