eli5: How do gamers figure out long cheat codes?

Question

eli5: How do gamers figure out long cheat codes?

In: 720

Answer 1

So besides the whole look at magazines back in the day and devs straight up telling people.

Another of the ways done back in the day was either have a code or similar in the credits as a reward for beating the game.

Or more rarely they could be found in the game itself somewhere when you did what nowadays is equivalent to achievements.