Which sources of cheats work?

[NeoVid]

I've been trying Gameshark codes for the games I'm emulating, but haven't gotten one to work yet. Are they not the right cheat codes for RetroArch, or am I typing them in with the wrong format?

I used the trick to download RA's official collection of cheats to the Steam version, but almost none of the ones on that list that I've activated have worked, either.

[Tapasvi]

There are different versions of roms. That's most likely the reason why it isn't working. Try another ROM or find the other codes for the same cheats.

[themazingness]

Not Gameshark, but there's a great utility called Game Genie Guy! that you can use to patch ROMs with Game Genie codes.

[NeoVid]

GGG looks like the sort of thing I was hoping for! Too bad it only goes up to the SNES era. If there's something like it for Playstation and on, it'd be perfect.

[Tapasvi]

Well, you can always make your own codes, it's fun. Have you ever wondered how these codes were made in the first place?
This was actually the feature of some GameSharks.

In Retroarch, this feature is in Cheats/Start or Continue Cheat Search. If you ever used Cheat Engine, it'll be very easy to understand. If you can't find the value, try changing the bittnes of searched value. Digits are straightforward to hack, gauges are through less/greater search, in some weird cases changed/unchanged.
In case of some difficult cheats you can refer to the gameshark code which isn't worked. The code contains the memory address, the value to set and sometimes conditionals, you can read what means what and dig in that direction.

[moonie]

gamehacking.org is my go to source. It lets you export codes in various formats too.