Encode and decode text with the Vigenère cipher, which shifts each letter by the letters of a keyword. Like the Caesar cipher it is simple letter substitution — fine for puzzles, but not secure encryption.
How to Use
- Type or paste your text into the input box.
- Enter a keyword of letters — it repeats along the message.
- Pick Encode to scramble text or Decode to unscramble it.
- Copy the result with one click, or clear to start again.
Key Features
- Live encoding — the result updates as you type.
- Any keyword — letters only; case does not matter.
- Encode and decode — reverse any Vigenère cipher instantly.
- Keeps letter case — capitals stay capital, punctuation untouched.
- 100% private — runs entirely in your browser; nothing is sent or stored.
FAQs
Is the Vigenère cipher secure?
No. Although it uses a keyword, it is still simple letter substitution and modern methods break it easily. Use it for puzzles and fun, never for real secrets.
How does the keyword work?
Each keyword letter sets the shift for one message letter, repeating from the start when the keyword runs out. Longer keywords make slightly trickier puzzles.
Can the keyword contain numbers or spaces?
No — only letters A to Z are used. Anything else you type in the keyword box is ignored automatically.
Is my text sent anywhere?
No. The cipher runs entirely in your browser and never transmits or saves your text.
Related Tools
Try these related tools: Caesar Cipher Encoder, ROT13 Encoder and Base64 Encoder.