CipherBox - Cipher and Code Encoder Decoder

Encode and decode secret messages using nine classical ciphers. Caesar, ROT13, Vigenere, Polybius, Affine and more.

CipherBox is a cipher decoder and code encoder for nine classical ciphers, plus automatic cipher detection, all in one browser extension. No accounts, no tracking, no data ever leaves your browser. Paste any unknown ciphertext into the Decipher Unknown screen and CipherBox automatically tries 349 combinations across Caesar, ROT13, Atbash, Affine and Rail Fence, scoring each against English letter frequency patterns to rank the most likely answers. It also detects Base64, hex, binary, Polybius and A1Z26 by pattern matching. Click any result to jump to that cipher tab with the key pre-filled, ready to encode a reply. Ciphers included: Caesar with full brute-force, all 25 shifts ranked by frequency analysis ROT13 Vigenère Atbash Rail Fence Polybius Square A1Z26 Affine with brute-force crack across all 312 valid key combinations Autokey Each cipher includes: Encrypt and decrypt A step-by-step walkthrough showing exactly what happened to each letter A plain-English explanation of the cipher's history and mechanics Perfect for: Puzzle solvers and escape room enthusiasts Geocachers, where ROT13 is widely used in puzzle caches Anyone interested in classical cryptography and secret codes Anyone who wants to encode a message a friend cannot immediately read No permissions required. No internet connection needed. Just ciphers. v1.1 Decipher Unknown, automatic cipher detection across 349 combinations, pattern matching for Base64, hex, binary and number codes, code refactor and various UI improvements. V1.0: First release