If I play slots, how does the computer decide who wins and when?

The online casino softwares operate with a random number generator (RNG), which will ensure the randomness of the results. The RNG is tested and certified by a special software testing company to prove its fairness. Because of its importance, this is also checked by the online gambling certificate issuer. In short, a computer chip is doing all the calculations, just like in a normal offline casino, where all slot machines have a chip inside that randomly decides the winners.