Caesar Cipher

Shift plaintext letters by a fixed number of positions.

Shift

Shift amount

The shift can be any whole integer and wraps around the alphabet.

Raw shift: 3 Normalised shift: 3 Plain A -> Cipher D Plain X -> Cipher A

Options

Preserve case

Keep punctuation & numbers

Remove whitespace

Group letters

Caesar encryption shifts each letter forward by k. Decryption shifts back by the same amount.

Output stats

Mode: Encrypt Effective key: shift=3 Letters processed: 0 Input chars: 0 Output chars: 0 Blocks: 0

Input

Output

Using This Tool: Guide & Notes Show guide

The Caesar cipher shifts every supported letter by one fixed amount. It is a simple classical substitution cipher and a good first example of how alphabetic encryption works.

How to use it

Choose Encrypt to shift plaintext forward, or Decrypt to shift ciphertext back.
Set the shift amount. Positive, negative, and large values are normalised around the 26-letter alphabet.
Paste text into the input box. The output updates using the current shift and formatting settings.
Use Load example to check the expected behaviour before trying your own message.

Options and settings

Preserve case keeps uppercase and lowercase letters in their original style.
Keep punctuation and numbers leaves spaces, digits, punctuation, and symbols unchanged.
Remove whitespace strips spaces and line breaks from the output.
Group letters formats the result into fixed-size blocks, which is useful for puzzle-style ciphertext.

Notes

A shift of 13 is ROT13. A shift of 26 returns the original text.
Caesar is easy to brute force because there are only 26 possible shifts.

Caesar Cipher: A Secret in Plain Sight

Why the world's easiest cipher to break is still the perfect place to start learning.

Read the article

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A note from the team

We build these tools because we love cryptography, encoding, and making difficult ideas easier to explore. If they've helped you, even a small coffee means the world to the project. Thank you!

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