Cipher tools and decoders
Classic ciphers for puzzles, escape rooms and spoilers. Most can find the key for you.
ROT13 undoes itself, so there is nothing to swap: the same button encodes and decodes.
Choose a conversion
Cipher tools
Start with the identifier
Know which cipher you're looking at? Go straight to its page. If you don't, paste the message into the cipher identifier. It tries every shift, the Atbash mirror and the common text encodings, then ranks the results by how much each reads like English.
Puzzle messages usually turn out to be one of three things: a shifted alphabet, which the ROT13 page handles at any shift from 1 to 25; a mirrored alphabet, which is Atbash; or not a cipher at all, but an encoding like Base64 or binary in disguise.
Substitution or transposition?
Most classic ciphers substitute: each letter is swapped for another, as in ROT13, Caesar and Atbash. Transposition ciphers do the opposite and keep every letter while scrambling the order, so a rail fence message has exactly the right letters in exactly the wrong places.
The difference decides how a message breaks. Substitution leaves letter frequencies intact, so counting letters gives the game away. Transposition leaves the frequencies looking perfectly ordinary while the words stay unreadable, and needs a different attack.
Questions
Which cipher is this message in?
Paste it into the cipher identifier. All letters with normal-looking word lengths suggests a shift or Atbash; digits and symbols suggest an encoding rather than a cipher.
Are these ciphers secure?
No. They're for puzzles and spoilers, and for escape rooms that need a lock anyone can pick. Every one of them falls to letter counting, a technique that's a thousand years old.
Why do some pages disable the swap button?
ROT13 and Atbash undo themselves, so there's nothing to swap. Each page says so where it happens.