Vigenère Cipher
Rijvs, Pkrensk!
Encode text with a keyword
The Vigenère cipher repeats your keyword across the message and shifts each letter by its keyword partner. Longer, less predictable keywords are harder to break than a single Caesar shift.
When to use this tool
Reach for the Vigenère cipher when a single Caesar shift is not enough — it uses a repeating keyword to shift each letter by a different amount, the classic step up for puzzle and CTF challenges or for teaching how polyalphabetic substitution works. Pick a keyword, then encode or decode on a single page.
Privacy and limitations
Everything runs locally in your browser; nothing is sent anywhere. This is a classical cipher, not real encryption — it only shifts A–Z and a–z, leaves digits and symbols untouched, and offers no autokey, running-key, or auto-solving features. You need the exact keyword to decode a message.