The first online slots casino appeared in 1996 at The Gaming Club and Intercasino, the first ever two online casinos. Simple 3-reel slots were used with limited functionality, similar to slot machines in Las Vegas, however, with the development of video slots, there are now hundreds of games available, many of which incorporate popular features such as bonus rounds.

In general, slots can be divided into the following categories: 3 Reel Slots, 5 Reel Bonus Slots, Progressive Jackpot Slots, Fruit Machines and Non-standard.

Online slots can even combine features from more than one category e.g. combines a progressive jackpot with a "free spins" bonus round. These games start at 1000 credits (dollars, pounds or euros) and rise gradually to be won by any player at any time on any bet, although the higher the bet the more chance there is of winning the jackpot.