Vigenère Cipher Encoder
What is Vigenère Cipher Encoder
The Vigenère cipher encodes text with a repeating keyword: each letter is shifted by the matching letter of the key, so the same letter can map to different ones depending on its position. That makes it far harder to crack than a Caesar cipher. This encoder applies your keyword instantly, keeps letter case, and leaves numbers, spaces, and punctuation untouched. Everything runs in your browser.
How to use
- Type or paste the text you want to encode.
- Enter a keyword, for example LEMON.
- Read the Vigenère cipher in the output box.
- Copy the result or share the link with the text filled in.
When to use it
Want a puzzle that resists a quick brute force? Encode 'Attack at dawn' with the keyword LEMON and the output only unlocks with that same word. It is a classic for CTF challenges, cipher puzzles, and teaching how polyalphabetic ciphers beat simple letter shifts. To read it back, use the Vigenère cipher decoder with the same keyword.
Frequently asked questions
How is Vigenère different from Caesar?
A Caesar cipher shifts every letter by the same amount. Vigenère uses a keyword, so the shift changes letter by letter and repeats with the key. That hides letter-frequency patterns and makes it much stronger.
Does the keyword need to be a real word?
No. Any sequence of letters works as the key. Longer, less predictable keys are harder to break. Non-letter characters in the key are ignored.
Is my text sent to a server?
No. Encoding happens entirely in your browser. Your text and keyword are never uploaded or stored.
Can I share this with my text pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens it sees your exact text ready to go. The keyword is never put in the link, so share it separately.
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