Vigenère cipher encoder and decoder
Make a repeating-key letter cipher for a puzzle or lesson.
No files selected
Repeats a letter key over A–Z; spaces and punctuation do not advance the key. For puzzles and learning only. It is not secure encryption. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Vigenère cipher encoder and decoder
- Enter your message, a key containing letters A–Z, and choose Encode or Decode. The key repeats across letters only; spaces and punctuation do not consume a key character.
- ATTACK AT DAWN with key LEMON becomes LXFOPV EF RNHR. Choose Decode with the same key to restore it.
Useful next steps
How to use it
Enter your message, a key containing letters A–Z, and choose Encode or Decode. The key repeats across letters only; spaces and punctuation do not consume a key character.
Try a small example
ATTACK AT DAWN with key LEMON becomes LXFOPV EF RNHR. Choose Decode with the same key to restore it.
What to know
Repeats a letter key over A–Z; spaces and punctuation do not advance the key. For puzzles and learning only. It is not secure encryption.