Where’s the fun in that? XD There are also plenty of resources on Tumblr and within the fandom, as well as on Google if you’re getting frustrated with cracking the codes and ciphers. This is also a good resource.
(Since I’m sure some people genuinely struggle with this and want to know how the ciphers actually work instead of just using an auto-decoder, I took the time to explain them)
How they work depends on the cryptogram being used.
Ceasar shifts all the letters of
the alphabet over a few spaces. It can change, but Gravity Falls generally does a 3 letter shift. So like, A would turn into C, B
into D, etc.
Atbash flips the alphabet backwards. So A turns into Z, B turns into Y, etc.
A1Z26 turns the letters into numbers. A is 1, B is 2, etc.
Vigenere is more complicated. It uses the same concept as the Casesar cipher, but uses a codeword to determine the shift. If you were going to code GRAVITYFALLS using the codeword PINES, for example…
P I N E S P I N E S P I (Codeword)
15 8 13 4 18 15 8 13 4 18 15 8 (How far to shift [A=0])
G R A V I T Y F A L L S
V Z N Z A I G S E D A A
So coding GRAVITYFALLS with the keyword PINES would create VZNZAIGSEDAA. To decode, you usually need to know the codeword, this code is extremely difficult to decode without it, but there are online programs that can try to decode it. This one is the best Ive found so far.
These are just the three used in the show (not counting the symbols, but that is usually just a substitution cipher, where they substitute letters for symbols instead, so no actual decoding, just figuring out what symbols are what letters).
Some codes in the show use more than one of these, though. So keep in mind they can be used together.