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Caesar Cipher

Caesar Cipher is part of Toolspire and is ready as soon as this page loads. The shift wraps inside the alphabet. Decoding is a shift of 26 minus the original shift, or a negative shift. It is a puzzle, not a secret.

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On this page

What you can do here

Any integer shift

26 is a full turn and changes nothing. 27 is the same as 1.

Negative shifts decode

Shift −1 undoes shift 1.

The wrap is in the detail

You can see the shift was reduced modulo 26.

The sequence

How to use the Caesar Cipher

  1. 1

    Type the text and the shift

    Abz with shift 1 is the check: Bca.

  2. 2

    Use 13 to match the ROT13 page

    Hello should become Uryyb on both pages.

  3. 3

    Decode with the opposite shift

    Bca with shift −1 returns Abz.

Worth knowing

  • Caesar Cipher on Toolspire: A shift of 1 turns Abz into Bca.
  • Z wraps to A. z wraps to a. Case stays.
  • A shift of 13 matches ROT13. Hello becomes Uryyb.
  • Digits and spaces are not shifted.

A wheel with 26 positions

The Caesar cipher adds a number to each letter’s place in the alphabet and wraps past Z. Shift 1 moves A to B and Z to A. Shift 13 is ROT13, which is why Hello and Uryyb agree with that page. A shift of 26, or 0, puts every letter back. Characters that are not letters are copied so the words stay separated. Anyone who can try 25 shifts can read it.

FAQ

Questions about Caesar Cipher

Where does Caesar Cipher run?

Caesar Cipher runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What is Abz shifted by 1?

Bca.

What shift is ROT13?

13. Hello becomes Uryyb.

How do I undo a shift of 1?

Shift by −1, or by 25. Both land on the same letters.

Are numbers encoded?

No. They are copied.

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