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Free Online Caesar Cipher

Encode or decode messages using a Caesar shift cipher with customizable shift offsets.

How to use & benefits of Caesar Cipher

Encrypt and Decrypt Classic Caesar Ciphers

The Caesar cipher is one of the earliest known cryptographic ciphers, named after Julius Caesar, who used it to secure military correspondence. It is a type of substitution cipher where each letter in the plaintext is shifted a fixed number of spaces down the alphabet.

Our free online Caesar cipher offers interactive shift options:

  • Custom Shift Key: Adjust rotation keys dynamically from 1 to 25.
  • Encoding & Decoding: Easily switch modes to decode encrypted ciphertext.
  • Preserves Formatting: Keeps spaces, digits, and line breaks intact.

Key Benefits & Features

✓
Adjustable Shift Keys

Configure custom letter rotation shift parameters (1-25).

✓
Symmetric Modes

Supports standard encryption shifts and decryption shifts.

✓
100% Free & Local

Processes messages locally in JavaScript, keeping strings secure.

How to Use the Caesar Cipher Step-by-Step

This utility runs entirely inside your browser using client-side JavaScript. We prioritize your security: none of your inputted text is logged or stored.

  1. 1

    Type your message text into the input panel.

  2. 2

    Configure the Caesar shift key using the number selector.

  3. 3

    Toggle the mode (Encode or Decode) and copy the result.

Practical Examples

Input Example

hello, Shift: 3

Expected Output
khoor

Frequently Asked Questions (FAQ)

How does a Caesar cipher work?▼

It replaces each letter in the text with a letter a fixed number of positions down the alphabet (e.g. with shift 3, A becomes D, B becomes E).

How do you crack a Caesar cipher?▼

Since there are only 25 possible keys, you can crack a Caesar cipher by testing all possible shifts until readable text appears.

Does it support negative shifts?▼

Yes, shifting left by 3 positions is equivalent to shifting right by 23 positions.

Explore category: Security & Cryptography
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