There are thousands of slots at casinos and online, with new slot titles being dreamt up all the time. While millions of people enjoy these games, few know how they work behind the scenes. On this page, we explain how slot machines work and the essential playing concepts that can make a difference for your bankroll.
Slots have evolved drastically from the first mechanical three-reel devices. These days, most slots are electronic, showing animated symbols on HD screens. Many have elaborate themes, some tie-in with popular music, TV or movie franchises. Bonus games might vary widely, though the underlying technology based on random number generator (RNG) software is standard for all games.
Below, you'll find out more about how RNG software works, key factors like return-to-player (RTP) percentages and the many varieties of slots available.
Also, we share how to take advantage of bonuses and loyalty schemes to get the best bang for your bucks from slot play. If you're looking for a spot to play slots online, we recommend the list below. Most of the casinos offer games similar to those you find in your local casino.
How does the RNG software work on a slot machine
Each time you press the spin button, the slot machine will generate a random sequence of numbers that determine the outcome of that spin. The RNG happens independently every single time you play.
While it can seem that sessions go in streaks, this is not the case. Each spin is an independent and random event. If you had hit the spin button a split second later, the RNG would have given you a different outcome. Both online slots and live casino slots use RNG software.
Auditing companies test the software to ensure the spins are fair and that (over the long run), the returns from each game are equal to the published amount.
Mechanical slots use a different system, which involves "stops" on each reel. Lower paying symbols will have a lot of stops, which means they occur (along with blanks) more frequently. Those with higher-paying, jackpot symbols will have the lowest number of stops, making it rare to line them up.
What is the RTP percentage?
Slots return most of the money put into them to players; however, this varies from 90% to 97%. You will often find "return to player %" in the help information.
The primary factor affecting the RTP of a slot is its denomination, which is the size of your stake per line. The range goes from penny slots up to dollars. While the stake might be the same (30 lines on a 10 cent slot equals $3, and three lines on a $1 slot also equals $3), the higher the denomination, the better the returns and all else being equal.
While this is a useful guideline, it is not enough information on its own to check whether a slot is worth playing.
How volatile are slot machines?
What you can't tell from the RTP% is how volatile an individual slot is. Some games give you regular, smaller payouts, while others pay big prizes though do it infrequently. This is known as the "variance" of a game.
The highest variance slots have big jackpots.
If someone wins a million occasionally, then the overall returns (to non-jackpot winning players) naturally need to be smaller to balance this. You'll find a lot of casino slots that pay small prizes of less than your spin amount, as well as bigger wins. These lower your variance, though not necessarily the overall returns.