How Slot Machines Work

Slot games are getting ever more complex, with bonus feature games, multiple win-lines and symbols on the reels with unique behavior. When you strip away the gimmicks and novelties, the way that these games work is actually very simple. This page will help you enjoy slot games while understanding the setup and logic which the games use to operate.

First of all below, I have used the example of a very simple 3-reel slot to explain the random number generator which lies behind all of today’s slot games. Video slots are then introduced, with their multiple win lines and special symbols. Bonus features, jackpots and special in-play features are covered after that. At the end of this page you will find a brief intro to payback percentages.

3-Reel Slots

Also known as traditional slots, the 3-reel games were derived from the original mechanical games. These slots have a single win-line, and you’ll need to line up symbols like cherries, bars or sevens to win. You often have a choice of 1 to 3 coins, with proportionally higher top payouts for adding the 3rd coin.

How the reels fall in modern games is determined by a random number generator (known as RNG). This software has no memory of previous spins. Each time you press spin a new random number is generated which determines how the reels will fall. These RNGs are tested by external organizations to prove that they are truly random.

Video Slots

Modern slots are far more complex than the 3-reel traditional games. These have 5 reels, usually over 3 rows, and can have anything from 9 through to 50 win lines. This adds some new flexibility to the game. You can choose both the number of win-lines and the size of the coin you bet for each line. For example a common max lines is 25, if you bet 5c per line then you are spinning for $1.25c each time.

The extra win-lines allow you to accumulate a lot of wins when the symbols do line up well. They also allow for symbols with special behavior to make the games more interesting. Wild symbols are often used. These can substitute for any other symbol to create a winning combination. Scatter symbols are also common in video slots. You get paid for these when 3 or more land anywhere on the reels – whether or not they are all on the same win-line. These symbols are often also involved in triggering bonus features.

Bonus Features, Jackpots and In-Play Specials

As video slots have become more complex, different entertaining feature rounds have been introduced into them. These range from free-spins through to separate games where you get taken out of the main reels view.

Free-spins were the original special feature. For example lining up 3 special symbols might have triggered the reels to spin 10 times without taking any coins. Wins were often multiplied in early versions of these features. More up to date slots also have these games; though usually combine them with some other effects. For example wild symbols which stay in place or the ability to re-trigger the free spins round if you hit certain symbols. Some slots give you a game where you choose from several objects to reveal the number of spins before the game starts.

The games have become very diverse and complex recently. These can involve simple ‘pick-em’ rounds, fights between superheroes, race games and many other novelties. What you should keep in mind is that the outcomes of the games are determined by the random number generator software. While you do interact with the game, skill is not usually a factor. See our slot reviews for details of the amazing bonus games on offer nowadays.

In reel behavior has also got complex and varied. The newest slots have a ‘cascading wins’ feature. Your win lines will explode, allowing more symbols to drop down which can create more win-lines. These can continue to explode, potentially giving you multiple wins from a single spin.

Jackpots have been a feature of slots since the start. Nowadays, this area has become more interesting too. Online slots are often linked between many casinos which offer the same titles. This allows progressive jackpots to reach millions of dollars in total. 6 and 7 figure payouts are happening online every month. Many casinos have their own smaller jackpots alongside the huge progressives.

Slot Pay Back Percentages

The final piece of the complex puzzle of how slots work is the payback percentage. This is the average return from the coins put into a machine. The usual range is 95% to 98%, with the higher scores better for the players. You can often find this information at your casinos website, along with external certification of their game fairness and integrity.

Chief Editor: Mike leverages his true passion for online gambling to create a uniquely informative site that takes players well beyond the standard fare in the industry.