Vigenère Cipher Encrypt & Decrypt
A keyword-based substitution cipher — stronger than Caesar. This tool does both encrypt and decrypt on one page — just pick a mode, paste your text, and click. Everything runs on your device, nothing is sent to a server.
Everything runs in your browser. Your data is never sent to our servers.
Example
Example Input
Hello (key: KEY)
Example Output
Rijvs
How to Use
- 1Choose Encrypt or Decrypt mode at the top.
- 2Type or paste your text into the Input field.
- 3If needed, open "More settings" to configure the key.
- 4Click the button (or press Ctrl+Enter) to process. The result appears in the Output field.
- 5Click Copy to copy the result, or "Swap input/output" to quickly reverse the operation.
About Vigenère Cipher
The Vigenère Cipher uses a keyword to shift each letter by varying amounts, based on the repeating key letters. This makes it much stronger than Caesar's fixed shift.
How it works: enter an alphabetic key in "More settings". Each text letter is shifted according to the key letter at that position (the key repeats across the text). Decrypt reverses the shifts.
For centuries Vigenère was considered "unbreakable" until the Kasiski/frequency-analysis methods were found. Today it is a classic for cryptography education and puzzles — not for modern security.
FAQ
Can this Vigenère Cipher tool both encrypt and decrypt?
Yes. This is a single page with a toggle — use Encrypt mode to transform text, and Decrypt mode to reverse it. No need for two separate pages.
Is my data sent to a server?
No. Vigenère Cipher is processed entirely in your browser. The text you enter never leaves your device.