Tries Base64, Base32, hex, binary, decimal codes, Morse, URL encoding, ROT13, Atbash and reversing, also two in a row, and ranks what reads best.
Procedure
How it works
Encodings are not ciphers: there is no key, only a public rule for writing bytes or letters in another alphabet. They are easy to undo once you know which one was used, and the alphabet usually gives it away. This tool simply tries them all.
Each decoder first checks that the input fits its alphabet (Base64 uses A to Z, a to z, 0 to 9, + and /; hex the digits 0 to 9 and A to F; Morse dots and dashes), then decodes. The outputs are ranked by a readability score: the share of printable characters, how English the letters look by quadgram fitness, and the share of letters.
Puzzles often stack encodings, for example hex written in Base64, so the tool can also try every pair of decoders. If nothing reads, the text is probably enciphered with a key: ask the cipher identifier.
Everything is calculated in your browser. Nothing you type leaves your device.