Vigenere cipher

Encode and decode a repeating-key letter puzzle.

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Vigenere cipher processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

Copy link includes the inputs you choose to share in the address. Anyone with that link can reopen them. Files and generated results are excluded. Password and key tools share settings only.

Your input

Repeating key

Options and local file

Direction

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Your result

Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.

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Updated 2026-09-20

Vigenere cipher explained

Shift each A–Z letter by the next letter in a repeating key. Only Latin letters advance the key; punctuation, spaces, accents and emoji stay unchanged. Encoding and decoding use the same key.

Next: Caesar cipher

A worked example

ATTACK AT DAWN with the key LEMON becomes LXFOPV EF RNHR. Decoding that result with LEMON restores the original.

Before you use the result

For historical puzzles and learning only. Repeating-key Vigenere does not protect secrets. The key must contain unaccented Latin letters.

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ToolOctopus. “Vigenere cipher.” Updated 2026-09-20. https://tooloctopus.com/vigenere-cipher.

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