The house edge on slot machines at online casinos will fall somewhere between 90-97%. The higher the Return To Player [RTP] percentage, the lower the house edge. Meaning you should look for slot games with the highest RTP. The RTP is the amount the machine has to return to the player/s over the course of an undefined length of time of play. Being undefined this could be a very long time and thus losing runs as well as winning runs can be experienced.