What is the Vigenere cipher?

The Vigenere cipher is a classic polyalphabetic cipher: each letter of your message is shifted by the letter of a repeating keyword, so the same plain letter can encrypt to different cipher letters.

Does the tool change my capital letters?

No. Capitals stay capitals, small letters stay small, and spaces, numbers and punctuation pass through unchanged. Only letters shift, using a case-insensitive keyword.

What makes a good keyword?

Use a keyword of letters only. The receiver needs the exact same keyword to decrypt your message.

Vigenere Cipher Tool

Encrypt or decrypt text with a keyword. Case and punctuation are preserved — only letters shift.

Message to encrypt

Keyword (letters only)

The keyword repeats over your message. Letters only, case does not matter.

Result

Worked example

Message HELLO with keyword KEY:

Message	H	E	L	L	O
Keyword	K	E	Y	K	E
Cipher	R	I	J	V	S

Each message letter is shifted forward by its keyword letter: H + K = R, E + E = I, L + Y = J, L + K = V, O + E = S. Decryption shifts each letter back by the same keyword.

How to use

Choose Encrypt or Decrypt.
Type your message and a keyword of letters only.
Press the action button — the result appears below and you can copy it.

Note: the Vigenere cipher is a learning classic, not strong modern security. Do not use it for anything that must stay secret.

Vigenere Cipher Tool

Worked example

How to use

Related Tools

Image to Text (OCR)

PDF to Text

Text to Speech

Speech to Text

Remove Duplicate Lines

Sort Lines A–Z