🔑 Vigenère Cipher

Encrypt and decrypt text using a keyword with alphabetic matrix shifts. Preserves case, ignores non‑letters — 100% client‑side, private.

📝 Plaintext / Ciphertext

🔑 Keyword (only letters, case‑insensitive)

📄 Result

📖 How to Use the Vigenère Cipher

Step 1: Enter your text in the left panel (plaintext or ciphertext).
Step 2: Enter a keyword (letters only, case‑insensitive).
Step 3: Click "Encrypt" to encode or "Decrypt" to decode.
Step 4: Copy the result, swap input/output, or clear fields.
Step 5: Use "Load Example" to see a demonstration.

💡 What is the Vigenère Cipher?

✔️ A polyalphabetic substitution cipher using a repeating keyword.
✔️ Each letter is shifted by a value determined by the keyword letter.
✔️ Non‑alphabetic characters (spaces, punctuation, numbers) are preserved unchanged.

💡 Pro Tip: For stronger encryption, use a long, random keyword. The Vigenère cipher is a classic educational tool – all processing happens locally in your browser.

🔒 100% client‑side • Your text never uploaded • Zero tracking • Instant encryption/decryption