You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.
Every online casino game utilizes a Random Number Generator (RNG). A reputable online casino developer will include an RNG in each game in order to ensure that the results are always completely random and legitimate.