A Crash Course in Slot Machines

A Crash Course In Slot Machines Video Slot Machines Collage Custom Image

Slot machines are the perfect American invention. The games are small enough to fit just about anywhere - these days, they can be designed to fit on a smart phone or tablet for play on the go. They're also bright and loud and (let's admit it) a little bit corny. Don't forget that every now and again they make somebody rich.

Not only were slot machines invented in America, they've been elevated by Americans to something like a high art. 80% of Americans gamble at least once a year. Since the majority of American casinos are heavy on slots and light on every other game, it's safe to say that a good chunk of the $120 billion Americans gambled last year was fed into a slot machine.

The purpose of this page is to fully educate you about slot machines by the time you've finished reading. In just a few thousand words, we can fully prepare you to sit down and play a slot machine game like you've been doing it all your life. Slot machines are deceptively-simple; walking into a casino with $100 and a desire to play slots is a great way to lose $100 in fifteen minutes.

This page will teach you about the history of slot machines, guide you step-by-step through the act of playing a slot machine, offer notes on how the machines work, discuss various in-game features, and share strategy tips for slot beginners.

First, an FAQ for people who are totally unfamiliar with slot machines.

An FAQ for Slot Machine Beginners

What is a slot machine?

Not many people have absolutely ZERO idea what a slot machine is. But we wanted to answer this question because we think it provides some useful context. Slot machines are those big boxy video game like gadgets on the casino floor with flashing lights at the top. They're the noisiest machine on the casino floor. Their cases are brightly-colored, densely-decorated, covered in symbols and numbers. Slot machines have spinning reels with symbols on them, and the spinning is just a little hypnotic. Slot machines are noisy games (increasingly computer-controlled) that offer long odds on some large payouts.

A plain definition of the phrase "slot machine" might look something like this: a slot machine is any device that allows real-money gambling, gives players 100% control of its operations, pays out winnings based on the series of symbols that appears on spinning reels. A long time ago, a slot machine was a coin-operated mechanical gadget with small prizes and just a few symbols. Back then, a pull of a lever would activate the game, set three reels spinning, and wins were automatically determined and paid out into a hoper.

That's all changed.

Slot machines these days may not have a lever to pull; having replaced it with a "spin" button or a touchscreen. They probably don't accept coins. Very few casinos host "old-school" machines that accept coins or require a real lever to start the game. You won't usually hear coins spilling into hoppers anymore, either. These days, prizes are tallied and paid out electronically, the same way the players place their bets.

The legal definition of the phrase would be more generic. It might say something like "A slot machine is any gaming machine that produces random symbol or number combinations, and which pays out varying amounts of money based on the combinations of those symbols." We based this on several state definitions of the phrase slot machine to avoid confusion. Don't forget that by most state law conventions, video poker machines are a sort of slot machine. Unlike slots, video poker machines require an added skill element, and the playing card symbol combos that lead to winnings are a bit more familiar than the random symbol combos of slot machines. But if you wipe all that away, the machines are almost identical.

Why are slot machines so popular?

For most players, slot machines are a cheap form of entertainment. Unless you're playing a high-roller machine or a game with an especially high per-spin cost, you're probably playing for something like $0.25 per spin. If you're playing at a machine with a 90% return percentage (at an average of 600 spins per hour) you're only looking at losses of $15 an hour. We'll teach you further down this page how to find games with much higher return percentages than that, to cut your hourly losses even more.

If you think of slot play as cheap entertainment, rather than a greedy gamble for money, it's easy to see why the games are popular. Modern game designers have incorporated aspects of video game design, including plots, licensed characters, and other features designed to keep players interested, like side bets, progressive jackpots, and gamble features. In other words, slots are popular because they're fun and they're designed to keep you playing longer and more often. Replay value is a big thing in the world of slot design.

Aren't these games rigged?

Slot machines hosted by legitimate casino operators are not rigged. How can we say that with such certainty? Because we understand how slot machines work. The mathematics that operates in the game's electronic brain dictates that, over time, the slot machine will always produce a profit for the operator. A slot machine is designed to win more than it loses. Even the "loosest" slot machine will still give the house some kind of advantage. A theoretical return of 99.9% still represents a profit (of 0.01%) for the casino hosting the game.

People think slot machines are rigged because they don't understand gambling math. There's also something called the Dunning-Kruger Effect at play. The Dunning-Kruger Effect refers to the tendency of amateurs to overrate their abilities. That's a serious risk in gambling, because every gambler thinks they're lucky or somehow special, and that they should beat the odds and win. The truth is that only a very few professional gamblers earn a profit over the long-run, and then only in games like poker and blackjack where skill can create a tiny advantage.

Aren't slots a waste of money?

We don't think so. Let's use the same example from above - someone placing $0.25 bets per spin on a 90% machine. Even losing $15 an hour, playing a slot for an hour is still cheaper than:

Once you've learned how to find slot machines with higher payout percentages, you can cut that cost even more. But for now, don't think of slot machines as a waste of money. Think of them as an inexpensive way to gamble in the casino.

Don't forget the impact of comps. We've earned free drinks and free meals for playing slots for as little as fifteen minutes before. The trick is to play the right game, get noticed, be respectful, and ask for what you want. Every comp you earn is like shaving a bit off the casino's advantage. For example, if you're losing $15 an hour, but you get a free cocktail every half hour, you're only really losing $5 an hour. Throw in a free room stay or a couple of free meals, and you can all but break even, given the right machine and a little luck.

A Crash Course in Slot Machine History

Slot machines would never have been invented if not for the invention of coin-operated devices in 1880. That was the first time that people could operate a gadget (temporarily) for the price of a coin inserted in its face. The slot machine also benefited from the expansion of America into the desert southwest and the far west.

Slot Machine Origins

America has always run on innovation more than any other substance. Coin-operated devices changed rapidly from their invention in 1880, that by 1888, machines which had the ability to pay out winnings with real coins were up and running all over the frontier. Those games weren't quite as popular as those which asked the operator of the saloon or restaurant hosting to game to handle payoffs on their own.

An immigrant, Bavarian-born Charles August Fey, put two and two together and created a game that we'd recognize today as a three-reel slot machine. This game had a built-in coin payout system, and was somewhat burglar-proof, which made it more tenable for saloon keepers to operate long-term. The popularity of the game forced Fey to start a new business, focusing on this game exclusively. This early game was more like video poker than a modern slot - symbols based on playing cards would line up to form poker hands. The better your hand, the higher your payout.

Fey's next machine abandoned playing cards (due to pressure from saloon keepers in Bible Belt states) in favor of pictures of random things. The game featured numbers, horseshoes, bells, and fruit images. The goal of the game was to line up three Liberty Bell symbols, hence the name of the game, The Liberty Bell.

Slot Machines Enter the 20th Century

How did slot machines survive the early 20th Century? This was a time of intense gambling scrutiny and increasing gambling prohibition. By the halfway point of the century, in 1951, pretty much every state in America outlawed all forms of gambling. The only place to gamble in America for the majority of the 20th century was the city of Las Vegas, which legalized gambling in 1931.

The slot machine's survival is due almost entirely to the phenomenon known as Las Vegas. From Charles Fey and company's simple mechanical games came more complex electro-mechanical slots in the 1950s. These games gave game designers new freedoms to create new styles of game. This led to a first renaissance in slot gaming, as machines with new forms of payouts, new jackpots, better graphics and effects, and bonus symbols were popped up throughout the 1940s and 1950s.

But it was the invention of the video slot machine in the 1970s that rocketed slot machines to their second renaissance and current dominance of the gambling marketplace. Video slot machines use simulated reels on a video display instead of actual reels spinning in a case.

The Video Slot

Believe it or not, video slots weren't popular at first. These games were new and unusual - you didn't pull a handle to start the spinning, and you didn't get to see or hear the physical reels spinning. There was something suspicious about the way the games paid out. People were convinced they were somehow getting ripped off.

A game designer in 1986 figured out a way to connect slots between casinos. The goal was to create a huge jackpot that players couldn't ignore. The huge jackpots produced by these linked games are constantly increasing, as more people pay into the network. That's why they're called progressive slots. With new record wins piling up on a daily basis, it's not hard to imagine why interest in the new style of slot games started to increase.

You could say that the video slot's invention was prescient for a different reason. By the time video designers were just getting really good at creating video-based slot games, around 1990, the first generation of hardcore video gamers were growing up and getting ready to do some gambling of their own. By creating gambling games that resemble console, computer, and standalone video games, designers had a natural hook for the new (young and often wealthy) gambling class.

A Crash Course in Slot Machine Mechanics

So how do modern slot machines work? What's behind these mega-popular games of chance?

What Is a Modern Slot?

If you walk into a casino in America right after you read this page, you're going to find mostly modern video games with computer-controlled random number generators for brains. Some US casinos still host classic games, but these are becoming less common as the years go by and demand for them decreases. Often, even these classic-style games are fully digital, displaying spinning reels but still controlled by a central computer system.

Virtual Reels

Instead of physical spinning reels, modern slots depend on a set of virtual symbol generators. These symbol generators work just like a reel, containing a specific number of "spaces" where the reels can stop. The thing to remember about modern slot games is that because virtual reels aren't limited in the number of symbols they can show, the same way a physical reel is, these games can be designed with multiple pay lines, multiple rows of symbols, and all sorts of special features and complex payout systems. When you have just three reels with five symbols on each reel, your ability to design a complex game is limited. That's not the case with modern slots.

Old-school slots use mechanical reels that spin, and the spinning and stopping is what makes the game random. In modern slots, randomness is still a big part of the game, except that it is added to the game in a different way. A thing (usually just a piece of software) called a random number generator adds randomness. Each of a modern game's virtual reels has specific stop positions programmed into the game, and the symbol that's directly associated with that stop position is established by this random number generator.

When you press the "Spin" button on the front of a slot, the random number generator tells the machine which symbols your random position indicate on the reels. Why do we even use symbols and all that, if everything is just math? I don't know about you, but I'd much rather watch The Simpsons running around on the screen getting into shenanigans than sit back and wait for a piece of software to pick random numbers.

Modern slots have benefited from the addition of new electronic and digital parts. The variety of game styles in today's slot marketplace is a direct result of the games' switch to digital brains. The same way that the first designers to create games for electro-mechanical slots could add complexity, modern game designers have completely changed the industry. Slots now have video game-like plots, fully-immersive special effects, 3D graphics, and all sorts of other bells and whistles to entice bettors and keep them in their seat.

A Crash Course in Slot Machine Styles

The evolution of slot machine games is such that every casino is likely home to a half-dozen different types of machines, all identifiable as "slots." This section covers the major categories of slots, to prepare you for a trip to your local slot paradise. Whether you play live or online, you'll need to understand these styles of slot machine if you're going to play without confusion.

Classic Slots

This phrase can mean two things. One type of classic slot is a game styled after traditional mechanical games. It's not likely that you'd find a real mechanical on a casino floor. You'd be more likely to see machine like this in the private collection of a gambling collector. We've seen a few mechanical machines as display items in casino and hotel lobbies, but never one that was actually accepting bets and paying winnings. Another type of "classic slot" is a modern game, with an RNG and electronic parts, designed to look and act like a real classic machine. That means these games are usually designed with three reels that really spin, as well as just one payline and a simple set of traditional symbols, like fruit and playing card symbols. These games are designed to suit a niche market among slot gamblers, people who have a taste for the simpler games and rules of classic slot machines.

Bonus Slots

The phrase "bonus slots" is a loose way to refer to any slot machine that offers a bonus game or other feature beyond traditional spin-the-reels-and-win play. Most modern games are technically bonus slots, though plenty of online and casino-based slots exist that don't technically reward any kind of bonus. Bonus games are those outside the scope of the traditional method of slot play, offering additional prizes or rewards. A side wager based on the flip of a virtual coin, a skill game asking you to test your skills with a virtual pistol, and a gamble feature offering double-or-nothing, they're all bonus games, and their presence makes whatever game they're on a bonus slot.

Progressive Slots

Slots linked to one another are called progressive slots. That's because their top prizes grow progressively larger as more and more people place bets and pay into the machine's network. Some progressive slots are linked up to other machines in the same casino. Other networks reach across multiple casinos. Online progressives are connected across thousands of miles via nothing more than an Internet connection. The possibilities are endless. How do progressives form those large jackpots? By slicing off a tiny bit of each player's wager and adding it to an ever-growing pool. When a player hits a specific combination, he wins some portion of that ever-increasing prize amount. The world's biggest progressive slot machine networks pay out prizes in the millions of dollars. These games are also governed by reset amounts - an amount of money the game starts at when it pays out and the jackpot starts growing again. Would you believe that progressive slots are responsible for some of the biggest casino payouts in history? One of the most notable examples of a large progressive prize comes from a lucky software engineer from Los Angeles who won $39.7 million on a $100 bet on a Megabucks machine at Excalibur in Vegas. He beat odds of 1 in 16.7 million to claim that life-changing reward.

Licensed Games

The first licensed slots appeared in the 1980s. It didn't take long for designers to realize the huge potential here. As it turns out, slot players are much more likely to try a game out if it features a familiar character, plot, theme, or even sound or visual effect. If you see a slot with the image of a familiar character, like Mickey Mouse, or a game that features a familiar set of rules, like Monopoly, you're probably looking at a licensed game. These games were first made popular in the casinos of Las Vegas, where competition for slot dollars forces innovation. Online slot designers have gotten in on the fun; now, some of the Web's most popular online slot machines feature familiar characters, video clips, and other effects.

Skill Games

Skill games are like slot machines with an added feature. In many states where traditional slot machines are illegal, so-called skill games (in which the player uses their skill to attempt to stop the reels at a specific spot) remain legal and are even prevalent. In casinos, skill games are usually kept near the banks of slot and video poker machines. You should think of these games as a combination of a video game and slot machine rules. It isn't that the element of luck has been entirely removed - instead, like with video poker, these are luck-based games with a strong skill element. Your ability to shoot apples off a shelf or make virtual basketball shots is directly tied to your winnings. These days, skill games make up a small portion of the total slot machine market, and you're not likely to find them in the big casinos of Vegas or Atlantic City.

A Crash Course in Slot Machine Strategy

Contained in this section is everything you need to know to approach slot machine play with strategy. Don't laugh - playing without taking the advice below under consideration is a recipe for losing more money in less time than you would if you'd paid attention. Before we get into the strategic advice, we want to take a moment to clarify a point we made earlier about return percentages:

A Word on Payback Percentages

All slot machines are programmed to behave according to the rules of the game designer. That means that even the slot machine's RNG (the random number generator that controls its operation) is programmed to spit out a specific number of random captures in a specific pattern. We say that to say this - a slot machine's payback percentage is a theoretical number and it isn't some sacred figure delivered from the mouth of a benevolent god. The payback percentage tells you what percentage of the money a person COULD play into it over an infinite amount of time is LIKELY to end up back in that theoretical player's hands.

Based on figures from casino gambler periodicals and other review websites, it's safe to say that the average slot machine is designed to payback somewhere around 90% of the money played into it over its lifetime. A 90% payback percentage means the machine pays back $0.90 for every dollar you play into it. This is considered a theoretical number, since to test it, you'd have to play out an infinite number of spins using an infinite amount of money. If you have an infinite amount of money, why are you wasting it on testing slot machine payback percentages?

We wanted to take a second to point out that a machine having a 90% payback percentage does NOT mean that you're going to walk away with 90% of the money you started with. Depending on the machine, a good portion of its payback percentage is dedicated to those huge (and rare) jackpot payouts. Slot machines are random, and that randomness means that some players will have good sessions, some will have bad session, and most will have mixed ones. Randomness is to blame, not bad luck or a bad machine.

Without further ado - our four tips for improving your basic slot playing strategy:

1. Join the Loyalty Club

Casinos make most of their money from slots fans. They love slots player. They also love to see them come back. That's why they're willing to reward slots players for their loyalty, the same way they reward the more serious blackjack or craps gamblers. Most casinos hand out plastic cards that you swipe before you play in order to track how much you're winning and losing. The house is tracking how much you're spending. If you spend enough, or if you become a regular visitor, the casino will notice that, and they'll give you something in exchange for what they call "loyalty."

Comps include everything from free drinks to free hotel stays, tournament entries, and other prizes. These comps are the only real incentive the casino has to entice you back, besides finding some way to make sure you win a jackpot, which isn't going to happen. If you choose not to join this club, you won't have your play tracked and it's unlikely that you'll ever get a comp of any kind. Remember that anything the casino gives you for free can be counted against your losses. Joining the loyalty club (or slot club or whatever they call it) is the easiest way to cut into the house's built-in edge. Remember, you don't have to win or lose a ton of money to earn comps. You just have to play consistently.

2. Avoid Progressive Slots

If you have a huge bankroll or a serious itch to do some long-odds gambling, by all means go ahead and play progressive jackpot games. Claiming a jackpot like the nearly-$40 million prize won in 2003 on a slot machine in Vegas would be nice, but it's probably not going to happen. There's no way to strategize your way to a progressive win on a slot machine. Chasing a progressive jackpot means waiting for your lucky day. If you have a limited bankroll or are interested in shorter odds, avoid progressive games altogether.

3. Bet the Maximum Amount

Slot machines allow a variety of wagers, from one unit activating a single payline to multiple units. The phrase "max bet" refers to the largest wager you can make on the machine. Your best bet, if you want to win the most money playing slots, is to always place the maximum wager for every spin. Why? The game's best prizes and bonuses are only available to max bettors. The trick is to find a machine you can afford. First, work out how much you can afford to spend per-spin. If you can only afford to pay $0.50 per spin, don't step up to a machine that maxes out at $5. You'll be spinning reels all day earning reduced jackpots, and you'll eventually blow your bankroll.

4. Play the Highest Denomination You Can Afford

Here's a good rule of thumb to remember - slots that cost the most to play give you better odds than the cheapest games on the floor. This is a general rule -we've seen a few games that don't follow this convention. But keep this in mind if you're looking for the best possible odds. This works at every level of wager - meaning you don't have to spend $10 per spin to get better odds. A move up from a nickel machine to a quarter slot will significantly increase your odds and your winnings-per-payout.


Slot machines are the mainstay of the US casino. American casinos keep their doors open thanks to slot machine profits. The trick to playing slots successfully is to stick to your win and loss limits, play machines with decent return percentage figures, and make sure you're stopping to enjoy yourself.

Slot machines are good cheap entertainment, more than the sum of their parts. Slots are available in all sorts of denominations, playable by cheapskates and high-rollers alike. Some slots pay huge jackpots in the millions or tens of millions of dollars. Others are humble affairs, styled after traditional games of the past. Slots are addictive, but they're also not that bad of an investment, in terms of player odds. /p>

We think slots are the best game on the casino floor because they're so adaptable. One game may tell the story of a popular movie, asking for $5 or $10 per spin bets. The machine next to it may max out at $0.50 per spin, paying humble prizes with simpler effects. You can have any experience you want with slot games. We hope that you'll go visit your local slot palace with your newly-acquired knowledge of the games. Just make sure you work for comps, stick to high-value games, and only play when you have a smile on your face.