Fair online casinos exist and of course they have counterparts which are cheats. Surprisingly both the mentioned versions can be offering the very same casino games which are provided by the very same parent software company because the places which provide the games sell a yearly license to more than just the one casino and as such stand to lose a lot of money if the games were ever proven to be anything but completely fair. In fact the rumor or gossip of the games not being fair could in some cases be enough to see that software company disappear never to be seen again. The integrity of online casino games will always have a shadow of doubt hanging over them the same as the video poker machines in the casinos in Las Vegas or Atlantic City still have their share of doubters as to whether the games are as fair as if you had been playing a regular deck of cards with a real dealer but for the majority of us it is an accepted given that the poker machines are giving us a fair-odds chance of winning.
This writer believes that if you are willing to trust the video poker machines at your local favorite gambling establishment whether that is a riverboat or Las Vegas, that you should have no problem trusting the online games at least until such time as they give you a reason to not trust them. I believe they will make believers out of most people those excepted being of exceptional bad luck because if you try the online casinos a few times they are going to prove that you do get a turn in the winners seat.
There is the fact that the games are using random number generator programs to provide game results, the gold standard in the industry for providing fair-odds games served in a completely and absolutely random manner. The way a RNG works is it has a list of all the possible outcomes for that particular game which it scrolls through at thousands of times per second and the instant the player presses the spin button, or deal or roll the dice button, that RNG stops scrolling through that list of possible outcomes and whichever one it lands on is what is returned to the player for a game result.
All the above said, I offer a personal experience as the reason I know the games are fair. I was playing video poker and increasing my credit values as I went along catching more wins and I had just increased the credit values from one dollar to the maximum this casino allowed which was five dollars per credit value. Incredibly the game dealt me a king high straight flush. The payout on it would match the payout on a royal flush at the credit level I started out wagering. The story gets much better than that however.