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Decision Tree

Walk through common clues to choose a cipher or code starting point.

This flowchart is a starting place to determine what cipher or code you are looking for. It does not cover every possible cipher or variation, but it is a useful first pass.

Is it repetitions of the following?

+, -, <, >, [, and ]

OR

Ook. Ook?, Ook? Ook., Ook. Ook., Ook! Ook!, Ook! Ook., Ook. Ook!, Ook! Ook? and Ook? Ook!

OR

.?, ?., .., !!, !., .!, !? and ?!

Try Brainf*ck & Ook! Code. These variations are all similar in their solve.

Is it repetitions of periods and spaces? Or number pairs with digits ranging from 1 to 5, such as 11, 23, 55, etc?

Try Tap (Knock) Code.

Is it repetitions of periods and dashes (possibly with a | or / between sets)?

Try Morse Code.

Is there anything in the description or hints that would suggest the text is a fiction or foreign language or alphabet?

Try the Code Tables directory or you can try Code Tables Examples where you can type in letters and see all matching code tables at once.

If you can't find the code here, try Omniglot which has an extensive selection of languages and alphabets as well.

Try substituting letters for the symbols and running it through a Cryptogram solver.

Did it work?

It could be a layered cipher. Take your results and start at the beginning again.

Are the letters just A, B, E, T or X? Or does it contain an upside-down 2 (

) or backwards 3 (

Try Duodecimal Numbers.

Does it have = or == at the end?

Try this base64 (mime) decoder.

Try this Rot47 decoder.

Did it work?

Does it contain numbers with the following characters? - † , * ‡ . $ ( ) ; ? ¶ ] ¢ : [

Try this Gold Bug decoder.

Does it have periods in odd places or does the letter "E" only appear at the end of the words?

Try this Dvorak decoder.

Is it composed of only dashes and ones?

Try the Spirit Rover DVD code or the spirit dvd substitution cipher on Rumkin.com.

Does it have \, |, or / in the text?

Is it composed of a number followed by \, |, or /?

Try the Vanity code method #4. On a keypad \ is the left letter for the given number, | the central, and / the right.

Try the following 4 code tools. Backslash Code, Five Needle Telegraph, Slash and Pipe Code, and Tomtom Code. All of these also use the \, |, and /.

It could be ASCII art. Take it into an editing program and play around with it.

Did it work?

Try substituting other letters for the numbers, letters and symbols and running it through a Cryptogram solver.

Did it work?

It could be a layered cipher. Take your results and start at the beginning again.

Are the letters just A, B, E, T or X?

Try Duodecimal Numbers.

Does the cache page mention a keyword, a password, a passphrase, a key or anything like that?

Find the keyword and run it through a Vigenère Cipher.

Did it work?

Try the Autokey Vigenère version.

Is it in two digit pairs with numbers plus only the letters A through F?

Try the Hexadecimal conversion tool.

Is it both upper and lower case letters as well as numbers?

Try this Base64 decoder.

Did it work?

Try running it through different number bases, at least Base 11 to Base 36.

Did it work?

Try the custom Geocaching.com Base 31 version. This version omits the letters I, L, O, S, and U.

Did it work?

Is the ciphertext arranged in an evenly spaced grid?

Try a Columnar Transposition cipher.

Did it work?

Try a Route Transposition cipher.

Did it work?

Is there anything in the description or hints that would suggest that a Cardan Grille might be in use?

Look for that Grille! Once you find it, try Dcode.Fr's online solver.

Is the number of characters in the ciphertext divisible by 4?

It could be a cryptographic hash or a public key encryption. You'll need to determine which one.

Is the number of letters such that they could be arranged in an evenly spaced grid?

Is the ciphertext short, as in 15 characters or less?

Try a Geohash decoder. One can be found in the coordinate converter.

Look back at the cache page for more hints. There are a lot of cipher types out there. Do a search for all of the supported cipher solvers.

Are the letters just A, B, E, T or X?

Try Duodecimal Numbers.

Does the cache page mention a keyword, a password, a passphrase, a key or anything like that?

Letters-only ciphers can be substitution, transposition, keyboard shifts, or keyword-based ciphers. Start with frequency analysis, then try the common letter-based tools.

Frequency Analysis Substitution Vigenere Columnar Transposition

Woohoo! Now it's time to go log that cache!