FreeDev Tools

Vigenère Cipher

Encrypt and decrypt with the Vigenère polyalphabetic cipher using a keyword.

Runs locally in your browser. Your input is not uploaded.

How to Use

  1. 1

    Enter your text

    The message to encrypt or decrypt.

  2. 2

    Set the keyword

    Letters only — it repeats over the message.

  3. 3

    Copy the result

    Decrypt mode reverses with the same key.

Frequently Asked Questions

Each letter is shifted by an amount determined by the corresponding letter of a repeating keyword — with key LEMON, the first letter shifts by L (11), the second by E (4), and so on.