List of cryptograms/Episodes

Caesar cipher
The Caesar cipher used in Gravity Falls substitute the original letter for the third letter before it. In the case for letters X, Y, and Z you must cycle through to the beginning of the alphabet.

Atbash cipher
Atbash ciphers are decoded by reversing the letter, an example includes that an A turns into a Z.

A1Z26
The A1Z26 cipher is a simple substitution cipher decoded by substituting the nᵗʰ letter of the alphabet for given number n.

Symbol substitution cipher
In 3, a symbol substitution cipher is used. The symbols are hidden on many pages of the journals. *Note: The symbols for J, Q, X, and Z are currently unknown.

Combined cipher
A combined cipher is a mix of two or more ciphers seen in the show. Only one such cipher has been seen at the end of "Gideon Rises." It's solved by converting to letters using the A1Z26 cipher, then flipping the letters with the Atbash cipher, and finally by using the Caesar cipher.

Number codes
These codes are solvable by taking the number beside a parenthesis as an episode number, and the other numbers beside them represents a letter in that episode's credits cryptogram.

Dipper's Guide to the Unexplained

 * The ceasar cipher combined, is a clue on how to solve the number code. Together you get, "FROM THE FIRST UNTIL THE LAST SEARCH THE CODES OF CREDITS PAST ONE MEANS ONE SO SEARCH THEM ALL WELCOME TO GRAVITY FALLS."
 * When the number codes are combined, you get the message: "I WAS SO BLIND. HE LIED TO ME. THE DARKNESS IS NEAR."