Fair question. Every spin is decided by an RNG - random number generator - that's running constantly, the moment you hit spin it grabs the current value. At a LICENSED operator the casino can't reach in and alter outcomes per player, the game logic lives with the provider (Pragmatic, NetEnt etc.), not the casino skin. And independent labs like eCOGRA and iTech Labs test the RNG and verify the published RTP. The edge is baked into the RTP openly, it doesn't need to be rigged on top.