TownCipher: Decoder Area

TownCipher: Decoder Area is a deep library of historical ciphers paired with a hands-on encoder and decoder for every one of them. Caesar, Vigenere, Pigpen, Playfair, Bifid, ADFGVX, Polybius, Beaufort, Bacon's biliteral, Trithemius, Atbash, Autokey, Scytale, Rail Fence, Columnar Transposition, Four-Square, Tap Code, Nihilist, Straddling Checkerboard, Book Cipher, One-Time Pad, Jefferson Disk, Hagelin, a simplified Enigma rotor simulator, and more — each presented with its history, its mechanics, and an interactive workbench where letters change as you type.

Beyond the workbench, wander a Cases Library of famous historical cipher events from Mary Queen of Scots' Babington Plot to the Zimmermann Telegram, meet a Pantheon of pioneering cryptanalysts, follow an interactive Timeline of cryptography from the Spartan scytale to the rotor machines of the Second World War, and solve a fresh Daily Decrypt with a streak that follows you across the seasons.

Climb the Mastery Belts in every cipher by completing graded Trials. Use the Sandbox to write your own encoded notes for friends. Tap any unfamiliar term to read its Glossary entry without leaving the page.