Some of the blog posts I’m most proud of here are the ones in my “ultimate guides” series. So far I’ve written ultimate guides to United States lottery games, greyhound racing, and Atlantic City casinos.
Today, though, I’m writing about something even bigger—the king of casino gambling games.
Today’s post is the ultimate guide to slots and slot machines.
My goal with this post is to share everything you might need to know to play slot machines intelligently in a casino.
Here are the topics covered in this post:
If you’ve read anything about antique slot machines or about the invention of these games, you’ve heard of Charles Fey. He was a mechanic living in San Francisco. In 1887, he invented a game with 3 spinning reels. Each of these reels had 5 symbols on them:
You’ll notice a playing card theme here, but you’ll also notice horseshoes—symbols of good luck. And the Liberty Bell is the symbol from which this prototypical slot machine game gets its name. The game originally required an attendant to pay off wins, but he continued working on and improving the machines. Eventually (by 1898), you could play a Liberty Bell slot machine and win a whopping 50 cents from the machine directly.
The games were quickly made illegal because of their gambling nature. But entrepreneurs are creative, and Fey (and other imitators) got around these restrictions by paying off winnings in candy. This is where we get the ubiquitous fruit and bar symbols seen still on these games today. The fruit symbols used to represent the flavor of the candy won. The bar symbols represented sticks of chewing gum.
In some ways, history keeps repeating itself. I live in Texas, and you’ll find slot machines called “8-liners” throughout the state. I’ve seen them in bars, in gas stations, and in “game rooms”. Since slot machines are (strictly speaking) illegal in Texas, these games don’t pay off in cash.
Instead, you get points which you can use toward prizes. I spent some time in a game room in a small town in Texas where you could literally cash in these points for canned goods like corn. They also had a cheap set of gardening tools available.
I’ve also played 8-liners in bars where if you won you had to visit the owner of the bar on Friday to pick up “an envelope”. This envelope had your cash winnings in it. But God forbid you ask for an envelope if the owner didn’t know who you were.
These are just examples from my personal experience of clever entrepreneurs skirting anti-gambling laws to continue to offer slot machine games to their customers. In that respect, things have changed little since the 1890s.
In fact, these gambling machines changed very little for decades, although they did become fixtures in the casinos. For years, these games were considered a distraction for the wives of the “real” gamblers—the men who were playing blackjack, craps, and poker. They were found in the places in the casino where the management thought they’d be more likely to attract the attention of these women.
Things started to change in the industry in the 1960s with the introduction of the first electro-mechanical slot machines. Bally Technologies invented a game called Money Honey, which incorporated a combination of electronic components. These gizmos enabled the designers to accept multi-coin bets. These games also ran faster.
Faster games with higher payouts increased the popularity of such machines, but they didn’t take over the casino floors immediately. This has been a gradual process that hasn’t stopped. But the invention of electro-mechanical machines like Money Honey was the first step in that direction.
The industry took off with the invention of video slots in 1979. The importance of the developments made in the 1980s can’t be overstated. The first of these was called Fortune Coin, and it was soon acquired by IGT, the largest manufacturer of casino games in the world. Believe it or not, it was initially distrusted by gamblers. They assumed that a game powered by computer animation would inevitably be rigged and impossible to win.
By 1986, these computerized games made it possible to link multiple games to the same ever-increasing jackpot. These games are now called progressive slots, and the first—and still most famous—example of these games is called MegaBucks. The jackpot for this network of games regularly surpasses $10 million.
These larger jackpots became available because of the lack of restrictions on number of symbols on each reel. With a mechanical slot machine, you’re limited to probably 20 symbols per reel max. And since such a game is mechanical, it’s hard to adjust the probability of a symbol coming up. Each stop had an equal chance of happening.
But with a computerized game, you can program one symbol to come up once every 20 spins and another to come up once every 40 spins. The games now use PARs sheets to delineate those probabilities. The designers and the casinos know what the odds are on these games. The public doesn’t have access to this information, though.
Over the last 30-40 years, slot machines have become the most popular game in the casino. Just a decade ago, you’d often see the following factoid on the Internet:
65%-70% of a casino’s revenue comes from the gambling machines.
But that’s changed. I read a book recently which claimed that in most casinos, slots make up 80% or more of that casino’s revenue.
This is a seismic shift in gambling practices in a casino.
In the 1990s, the Internet became a thing. It didn’t take long for gambling entrepreneurs to realize that you could use similar computer technology to offer the same kinds of games over the Internet. The Web also allowed these operators to offer their games to players in areas where gambling was illegal. (Remember—that’s a tradition in the industry.)
The thinking is that an offshore casino is regulated by the laws where it’s located. If gambling on the Web is legal in Costa Rica, for example, it’s legal for someone in Texas to gamble online there. Their contention is that the wagering is taking place where the server in Costa Rica is.
The federal government in the United States takes a less enlightened stance on this idea. They’ve made it clear that offshore companies offering gambling games to United States players are breaking the law. They’re less close-minded about whether the players are breaking the laws.
As Criswell points out in the great Ed Wood movie Plan 9 from Outer Space, we’re all interested in the future, because that’s where we’re going to spend the rest of our lives. But who knows what the future holds for slot machine gambling?
It’s clear to me that we’ll continue to see innovations which make these games even more compelling and addictive. The legal climate in the United States seems to be trending toward legalization. Just in my own lifetime, I’ve seen gambling become something that people had to fly to Nevada or to New Jersey to do. Now I can just drive an hour north to the Winstar Casino to spin the reels and try my luck.
Slot machines are going to continue to become more interactive and profitable for the casinos. Eventually, I’m going to predict that they’ll become too interactive and addictive. At that point, the government might start restricting gambling on a legal basis again. The pendulum seems to swing back and forth with such things, at least in the USA.
Most of the research for this section was done using Wikipedia.
Slot machines are the easiest games in the casino to play.
You insert money, push a button or pull a lever, watch the spinning reels, listen to the sounds, and collect your winnings (if any).
In fact, slots are so simple to play that it almost seems silly to write a guide on the subject.
But like any other gambling activity, playing slots has subtleties that aren’t apparent.
In practical terms, here’s what you need to know about playing these games.
When you’re looking at one of these games, you’ll notice that it looks a lot like a traditional coin-operated video game in an arcade. Only most slot machines have a lever on the side.
And in fact, most modern slots have more in common with video games than anything else. 50 years ago slot machines were mechanical and powered by springs and gears, but modern slots are powered by computer programs and video screens.
When you’re facing the machine, you’ll see the name of the game and its logo at the top. Underneath that are the spinning reels that make up the game. On many modern games, these spinning reels are animated.
If it’s an old-school machine with actual physical spinning reels, a pay table will be printed on the glass above or to the side of the spinning reels. This pay table shows the possible winning combinations of symbols and how much they pay if you hit them.
On newer machines with animation, you can access the pay table via the controls on the screen. (The controls and the pay table are both part of the animation, usually, although some machines have physical controls on the console.)
Most slot machine games still have a lever on the side, but it’s just for show. When slot machines were purely mechanical affairs, you’d use the lever to start the reels spinning. Now you have the option of pushing a button on the console to start the reels spinning. There’s no advantage to using either option, although you’ll play slower if you use the lever instead of the button.
Beneath the spinning reels is where you put your money into the machine. Some modern machines only have bill changers, but some still also accept change in a coin slot. When you input your money, the machine updates electronically and displays how many credits you have.
Beneath where you input the money is a metal tray called a hopper. In the old days, this is where your winnings would spill out. They were paid in coins, and casinos used to have big plastic buckets located throughout to use to put your coins in.
Most modern slot machines use a ticket in/ticket out system now. You cash these tickets in at the cage in the cashier area, just like you would cash in clay casino chips. The bill changer on modern slots will also read your tickets—you can insert them just like cash.
The ticket in/ticket out system has a lot of advantages for the casinos, the biggest being breakage. That’s just a fancy word to describe tickets that don’t get claimed. Many gamblers don’t want to waste time standing in line at the cage to cash in a ticket that might only be worth a couple bucks.
The casino gets to keep this money if the players don’t claim it.
And a couple of bucks per person matters a lot when you’re dealing with thousands of people per day.
The actual mechanics of playing are simple, though. You insert your money, choose how much you want to wager per spin, and wait to see what your results are. When you’re ready to cash out, you push the button to cash out and take your ticket.
Some games do pay more if you play max coins, but others don’t. Read the pay table to find out beforehand. If the game has higher jackpots for playing max coins, you’ll probably want to do so. If you can’t afford to, you should move to a lower denomination machine.
These games are played in the same way regardless of where the casino is. Slots in Las Vegas play just like the games in Atlantic City. The games in Reno are the same, too. The insides might work differently from one locale to another, but that difference is more-or-less opaque to the player. I’ll write more about the different kinds of innards slots have in the next section.
I referred frequently to this article when I researched this section.
These games aren’t just played in the United States. They’re popular in other countries, too. In fact, in some countries (ahem, Australia), they’re practically a national pastime.
But most countries call them by another name.
In England, they’re called “fruit machines”.
In Australia, they’re called “pokies” (short for “poker machines”).
In Norway, they’re called “kronespill”.
In Scotland, they’re called “puggys”.
In Canada (and often in the U.S.) they’re called “slots”.
They all feature spinning reels. That is, in fact, the defining aspect of such a game.
But they also feature different gameplay options and variations depending on where you live.
Fruit machines, for example, differ slightly from regular slot machines. In fact, they resemble the 8-liners found in bars in Texas. They resemble video poker machines, in a sense. That’s because they almost always give you the option to hold some symbols and take another spin on some of the reels. This doesn’t imply that skill helps in any way. The results are still randomly controlled by a random number generator, and no amount of so-called strategy will improve your odds.
Pokies, on the other hand, usually feature a massive number of pay-lines and lots of bonus features like scatters, wild symbols, and bonus games. The newest innovation in pokies are the games with 243 ways or 512 ways to win. These basically eliminate the concept of pay-lines entirely. Any winning combination from left to right results in a win.
I should point out to that one of the biggest and most popular gambling destinations in the world now is Macau. But slot machines aren’t a big draw there. In fact, baccarat occupies the position in the casinos there that slots hold here in the U.S. Over 80% of a Macau’s casino revenue is generated from baccarat, not slots. That’s a significant cultural difference, to be sure.
I consulted this page when researching this section of the post.
The original slot machines developed at the turn of the last century were mechanical devices with actual metal reels inside them. When you pulled the lever, the springs set those reels to spinning. Symbols were printed on the front of the reels, and when they lined up, you got paid off.
For example, you might put a penny into such a machine, pull the lever, and see three cherries line up across the center of the reels. That line across the center of the reels is called a pay line.
Modern slot machines often have multiple lines, but you pay to activate each line. Old-school games had only three reels and one payline.
These kinds of games still exist, but they’re no longer powered by springs and reel stops. Their results are determined by a computer program called a random number generator. These are called classic slots. They might seem boring compared to some of the newer, flashier, and glitzier games.
But they usually offer the best odds in the casino (at least as far as slot machines go).
Newer slot machines also often feature five reels instead of three. To accomplish all these extra reels and pay lines, the slot machine manufacturers use animation and computer programs. Five reel slots and multi-line slots are usually video slots. That just refers to what the game looks like.
These games often include all kinds of bonus features and games. Some of these bonus games even have skill elements. Others are completely random.
A good example of a game with a bonus feature is Wheel of Fortune slots. If you’ve spent any time in an American casino, you’ve seen and heard this game. It’s based on the popular game show. If you get certain combinations of symbols on the screen, you get to spin the wheel.
On most Wheel of Fortune games, the wheel is smaller and is located on top of the machine. I’ve seen versions that are huge and allow multiple people to sit around the wheel itself. Most players love getting to spin the wheel.
And of course, you get a bonus payout based on where the wheel lands.
These games often also include wild symbols. If you play poker, you’re probably familiar with the concept of a wild card. It’s just a card that can substitute for a card that would make a winning hand.
A wild symbol on a slot machine game works in the same way. It substitutes for a reel symbol that you would need to have to achieve a winning combination.
Modern slots also often include scatter symbols. These are symbols which don’t need to be on any specific pay line to achieve a winning combination. No matter where they appear on the screen, if the right number and type of scatter symbols show up, you get paid off.
Slot machines differ from most other gambling games. You can easily list the number of poker variations or blackjack variations on a single page. But slots come in a staggering array. That’s because dozens of manufacturers create new games constantly.
In fact, you can find several ways to categorize these games. Below are some of these ways:
Legally, slot machines can be categorized by how their algorithms work. These categorizations are Class II and Class III. They matter because they affect which kinds of games the casino can legally offer. In states which allow tribal casinos, the restriction is often that they can only offer Class II slot machines. These games are based on a bingo algorithm. All the games are networked together with a central computer which is constantly running bingo games. The payouts are based on the bingo results, and the spinning reels are just for show. Class III slot machines, on the other hand, have individual random number generators inside each machine.
Progressive slot machines have jackpots that grow constantly while you play. You’ll see a jackpot ticker at the top of such a machine which tells you what the top jackpot is. Flat top slot machines, on the other hand, have a fixed top jackpot.
Traditional slot machines have 3 reels and usually 1-3 pay-lines. These games look mechanical, even though the results are still powered by a computer program called a random number generator. Video slot machines usually have 5 reels (or more) and at least 5 pay-lines. They cost more to play because you pay to activate each pay-line. But you have more opportunities to get at least small wins.
Video slot machines are usually the games with all the bonus features like bonus games, scatter symbols, and wild symbols. All these bells and whistles result in lower payout percentages for the player, though. You have a choice. Play the fancier, more fun game. Or play the more boring game which provides you a better chance to win.
I leave it to you to decide which of those options is better for you.
I read a book about gambling once that compared the popularity of slot machines with a quote from the Beatles. At one point, they claimed to be more popular than Jesus.
And if slots are that popular, specific games occupy high positions of popularity within the category. This section of the post looks at the most popular games and how they got there.
Wheel of Fortune slots are the undisputed kings of the gambling machine sections of casinos in the United States. I read a book about slots recently that claimed that IGT, the game’s manufacturer, were so eager to duplicate this game’s success that they surveyed the players to find out why it was so popular.
They got a variety of answer, of course. But one answer was common.
Most of the people who loved Wheel of Fortune slots said that the game reminded them of watching the game show on TV with their grandmother when they were young.
How can you beat that as a formula for success?
In fact, Wheel of Fortune isn’t just a single slot machine game anymore. It’s a brand. Lots of different games use the branding, and each of them has different gameplay features. They all have two things in common, though:
Wheel of Fortune isn’t the only game to borrow elements from a popular game show. You’ll find plenty of them scattered throughout the casinos: The Price Is Right, Jeopardy, The $20,000 Pyramid, Deal or No Deal, and Who Wants to Be a Millionaire have all spawned slot machine games.
The Simpsons slots are like that, too. It’s more about branding than specific gameplay features. Multiple slot machine games share the branding, sound effects, characters, and iconography. The newest version is a big flashy monstrosity of a game. The TV show has been on the air for over 27 years now.
Notice a trend yet? Tapping into existing intellectual properties and brands is a smart move for game manufacturers and casinos. People love familiarity. You’ll find that most of the most popular gaming machines tap into this tendency.
And The Simpsons isn’t the only cartoon to spawn its own gambling game. The Pink Panther has been popular for years. South Park slots are also hugely popular. At one time, using a cartoon as the basis for one of these games was controversial. The regulators felt like this was a means of enticing under-age gamblers. But most modern cartoons aren’t even aimed at children.
Elvis slots are a big deal, too. Like the other games I’ve listed, several different machines share this branding. You can find slot machine games featuring skinny Elvis, fat Elvis, and Elvis singing different songs. (“Burning Love” is a favorite.)
He’s probably the most iconic singer to have a popular slot machine game, but other singers are in on the action, too. Dolly Parton slots are popular. Cher has her own slot machine, too. You can even find slots based on Hee-Haw, a country western music themed variety show that was on the air for decades.
In short, anything that summons nostalgia among the right demographic is a potential theme for a popular gambling machine. The more popular the brand and intellectual property, the more popular the game.
A slot machine tournament is an opportunity for you to compete against other gamblers. It’s also an opportunity to get a good little bit of action without spending a lot of money.
Here’s how most slot machine tournaments work:
You pay an entry fee. For that, you get a certain number of credits on a slot machine. The other players do likewise.
When the tournament starts, the casino sets a timer, and you get to make as many spins as possible before one of the following happens:
When the timer runs out, the player with the most credits is the winner.
Usually this gives you an opportunity to get a large payout for a low buy-in. Many of these tournaments are offered as freerolls by the casino to attract new customers.
I researched some of the information for this section using this page.
All casino games have this in common—they pay off less than the odds of winning. For example, if you place a bet that pays off at 10 to 1, you can bet that the odds of winning are worse than 10 to 1. The casinos are in business to make a profit. This mathematical edge is how they do it.
Here’s a specific example of how that might work with a simple slot machine game:
You’re playing a game with 3 reels and a single payline. Each reel has 8 symbols on it. The probability of getting a specific symbol on a specific reel is 1/8. The probability of getting that symbol on all 3 reels is 1/8 X 1/8 X 1/8, or 1/512. This means that the odds of winning are 511 to 1. If that bet pays off at 500 to 1, the casino expects to win money in the long run.
Let’s assume you’re playing for $100 per spin. You lose $51,100 on your losing spins. But you win $50,000 on your winning spin. Your loss is $1100 on the 512 spins, which means you lose an average of $2.14 per spin.
This means the casino has an edge of 2.14% on this bet, and the payback percentage (the amount they expect to pay back on every bet) is 97.86%.
Of course, modern slot machines are more complicated than this. They usually have more than 8 symbols on each reel. They might have 15 or even 20 symbols.
And since they’re not mechanical but computerized, they can weigh the probabilities of some symbols coming up differently than others. Some symbols might come up an average of once every 40 spins, while others might come up an average of once every 10 spins.
These numbers are all determined by the designer and the PARs sheet for the game. But the casino and the manufacturer know the exact expected payback percentage for every slot machine on the floor.
In fact, in almost every case, the gamblers don’t have the information needed to calculate what the payback percentage is for a specific game.
This makes the slot machine the only game in the casino where it’s impossible for a player to know what kind of house edge he’s facing.
I used some information presented on Gamblers Bookcase when researching this section.
The best slots games for the smart players are no slots games at all. These games always have a house edge that can’t be overcome. If you play any of these games long enough, you’ll lose all your money.
So some games can be considered less worse than others, though. The lower the house edge, the better. At the same time, if a game has a low payback percentage but isn’t fun, it’s probably not worth playing, either.
What’s a smart slot machine player to do?
Here are some tips about which games, in general, offer the best odds. I also offer some personal observations about how useful each tip is.
You can also find plenty of bad advice about how to choose the best slots games. Below are some examples of advice that isn’t accurate:
A lot of the details about improving your chances of winning at slots was found at Michael Bluejay’s excellent page on the subject.
Per my rigorously scientific (not) research on Google and Bing, these are some of the most commonly asked questions about slots and slot machines. Lots of people seem to want to know the answers to these questions. I’ve answered them succinctly and included links to other resources that answer them in more detail.
Okay, so this one might not be a word-for-word question many people ask, but this is the one that gets to the point most people care about. How can you win at slot machines? Is there a smart way to play?
The short answer is that none of the slot machine strategies you’ll read about online are winning strategies. Slot machines—and every other casino game, for that matter—have an unassailable house edge. Mathematically speaking, nothing you do can improve your odds of winning.
The best you can do is try to choose games with a low house edge. You’ll at least get more entertainment for your money.
But if you play long enough, no matter what strategies you use, you’ll eventually lose all your money.
You can find comprehensive information about slot machine strategy in this page on this site.
Yes, you can play slot machines for free, but not at traditional brick-and-mortar casinos. Free slot machine games are available at most online casinos. These companies want you to try free versions of their games, hoping that you’ll upgrade to playing for real money.
You can also buy software and download apps that have free slot machine games.
I’ve never seen the point in playing such a game. After all, aren’t you just pushing a button and watching a meaningless animation?
The only thing that gives a slot machine game any meaning at all is the money that you have on the line, isn’t it?
The only reason I can see for playing a free game is to try out the casino software to see if you think you’ll want to play the real money games there.
Some people are from a school of thought that says you can’t be addicted to slot machines because you’re not ingesting anything into your body. Slots aren’t like drugs or alcohol. How could you become addicted to them?
Those people are wrong.
Addiction is more complicated than that. Gambling game designers do their best to make these games addictive.
If you know anything about behavioral psychology or how the brain reacts to video games and gambling games, it doesn’t take you long to realize that slot machines are addictive.
Does this mean you’ll become a mindless slave to these games if you play them?
Addiction is more complicated than that, too.
The best thing you can do is look for warning signs that your gambling has gotten out of control. The most important warning sign is a lack of joy in the activity.
If you’re compelled to play these games but don’t enjoy them, you might have an addiction.
Read a detailed guide to gambling addiction in general here on this site.
The answer to this depends on where you live. In some states, slot machine ownership is completely illegal. In others, you’re allowed to own such games if they’re old enough to qualify as antiques. How old such games must be varies based on state law. But in all states, you must have a gambling license to own such a game and offer real money play to customer on it.
You can find a more detailed question and answer section elsewhere on this site.
The random number generators on a slot machine are programmed to pay off at a certain percentage over the life of the game. But in the short run, anything can happen. Casinos understand this. They don’t need to re-program these games. They just let them run until the long-term expectation kicks in.
I hope you found this definitive guide to slots and slot machine helpful.
Would you do me a favor now?
Leave a comment below and let me know what you think of this guide to slot machines.
What did I leave out that I should have included?
What questions do you have that I didn’t cover?
Did you see any mistakes?
I’d be grateful for the feedback, and I’ll update this guide accordingly.
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