Slot machines have changed from simple mechanical devices with a few physical reels into software games with thousands of possible win combinations, bonus rounds, progressive jackpots, and changing reel layouts. The biggest changes were not just visual. Each major generation changed how prizes were calculated, how wins were triggered, and how much information players could see about the game.
As part of our wider slots knowledge and education section, this guide follows that evolution from the first coin-operated machines to modern online slots and asks a more useful question along the way: what actually changed for the player?
What Did the First Slot Machines Look Like?
The earliest ancestors of modern slots were mechanical gambling machines built around physical drums, cards, coins, and levers. They looked very different from today’s five-reel video slots, but they introduced the basic idea of paying to generate an uncertain result.
One famous early machine was created by Sittman and Pitt in New York during the 1890s. It used five drums carrying playing-card symbols and worked more like a mechanical poker game than a modern slot.
Players inserted a coin and pulled a lever to spin the drums. Prizes were often provided by the business hosting the machine rather than automatically paid in cash.
Why Was Charles Fey’s Liberty Bell So Important?
Charles Fey’s Liberty Bell helped establish the basic three-reel slot design and automatic prize payment that became central to later machines. Instead of trying to copy a full poker deck, the machine used a much smaller group of symbols that made winning combinations easier to calculate and pay automatically.
Fey developed his machines in San Francisco in the late 1890s and became one of the most important figures in early slot-machine history.
The Liberty Bell used symbols such as horseshoes, card suits, and bells. Landing the right combination produced a mechanical payout.
The big innovation was not flashy graphics. It was automation. The machine could take the bet, determine the result, and pay a prize without somebody behind a counter deciding what the player had won.
How Simple Were Early Slot Prizes?
Early mechanical slots had tiny prize structures compared with modern games because physical reels limited the number of possible combinations. Fewer reels and fewer symbol positions meant much simpler mathematics.
Imagine a very simple three-reel machine where each reel has 10 equally likely stopping positions.
The total number of possible reel combinations would be:
10 × 10 × 10 = 1,000 combinations
If only one combination paid the top jackpot, a simplified model would give that result a 1 in 1,000 probability.
Real mechanical machines could use different reel strips and symbol frequencies, but the example shows how quickly reel mathematics develops from a simple physical layout.
How Did Fruit Symbols Become Part of Slot History?
Fruit symbols became closely linked with slot machines during the early 20th century, when some machines offered prizes such as gum or merchandise instead of direct cash payouts. Cherries, lemons, oranges, plums, and BAR-style symbols later became visual traditions that survived long after the original prize systems disappeared.
That is why modern digital slots still use fruit symbols even though there is no fruit-flavored gum waiting behind the casino counter.
The symbols became part of the language of slot-machine design.
How Did Slot Machines Become Mainstream?
Companies such as Mills Novelty Company helped turn slots from unusual inventions into widely installed coin-operated machines. Machines appeared in bars, stores, bowling alleys, and other businesses as the format became easier to manufacture and operate.
The Operator Bell became one of the important early commercial machines associated with this period.
At this point, the basic slot experience was already recognizable: insert money, activate the machine, watch the reels stop, and receive a prize if the right symbols appeared.
What Changed When Slots Became Electromechanical?
Electromechanical slots allowed manufacturers to add more complex features while keeping the familiar reels and lever. Electrical components could control parts of the machine that had previously depended entirely on gears, springs, and other mechanical systems.
Bally’s Money Honey became an important machine in this transition during the 1960s. It is widely associated with the move toward electromechanical slot design.
The lever remained, but the technology behind the game was changing.
This mattered because electrical systems gave designers much more freedom over payouts, lights, sounds, and game behavior.
Why Did Video Slots Change Everything?
Video slots removed the need for every reel and symbol to exist as a physical object. Once the game could display reels electronically, developers gained far more freedom to build unusual layouts, bonus screens, animations, and mathematical models.
Fortune Coin was involved in early video gambling development during the 1970s, a period that also helped lead toward what later became International Game Technology. UNLV oral-history material places Fortune Coin’s video gaming development in the late 1970s.
The key change was bigger than replacing spinning metal with a screen.
Once the screen stopped being limited by physical reels, a slot could become a piece of software.
How Did Video Slots Change the Number of Possible Outcomes?
Software allowed slot designers to separate what players see from the much larger mathematical system behind the game. A five-reel screen does not mean the game is limited to the simple number of combinations visible on those reels.
Consider a simplified physical game with three reels and 20 stops per reel:
20 × 20 × 20 = 8,000 possible combinations
Now imagine six reels where each can display seven possible symbol positions:
7 × 7 × 7 × 7 × 7 × 7 = 117,649 combinations
That number, 117,649, will look familiar to players of modern Megaways games.
The move to software made mathematical complexity far easier to build.
When Did Progressive Jackpots Change Slot Prizes?
Progressive jackpots changed slots by allowing a top prize to grow instead of staying fixed. Bets from qualifying play can feed a jackpot pool until one player triggers it.
This eventually allowed slot prizes to reach levels that would have been impossible for an isolated mechanical machine.
Modern progressive networks can connect games across many casinos. Games Global currently describes Mega Moolah and WowPot as major progressive networks, and reported that the two networks paid more than €155 million during 2023.
You can explore more examples in our guide to slots with progressive jackpots.
How Much Bigger Did Slot Jackpots Become?
Modern networked jackpots made multi-million-dollar slot prizes possible because thousands of players could contribute to the same progressive system.
Mega Moolah provides a useful example. Games Global says the original game entered the progressive market in November 2006 and had awarded more than €700 million across its network by early 2024. In that same year, one player won €6,689,308 from a €3 wager.
In June 2025, another Mega Moolah player won almost £11.5 million.
Compare that with the fixed coin payouts of early mechanical slots and the scale of the change becomes obvious.
What Changed When Slots Moved Online?
Online slots removed the need for players and games to exist in the same physical casino. Software developers could distribute one slot across many operators and countries, while players could access huge game libraries from a computer.
This also made it much easier to release new themes, mechanics, bonus systems, and progressive networks.
Instead of a casino floor having room for a few hundred physical machines, an online casino could offer thousands of titles through one interface.
The physical limit on choice largely disappeared.
How Did Online Slots Change Player Information?
Modern online slots can give players far more technical information than early machines ever displayed. Game screens and provider pages may show RTP, volatility, max win, betting range, paylines, ways to win, and feature rules.
For example, NetEnt currently lists Starburst with a 96.08% RTP, 23% hit frequency, 800x maximum payout, five reels, three rows, and 10 paylines. It also explains its expanding Wild and Respin mechanics.
An early mechanical player could see symbols and a prize table.
A modern player can sometimes see a large part of the game’s mathematical profile before placing a bet.
How Did Bonus Features Change Slot Gameplay?
Bonus features turned slots from single-spin machines into games where one paid spin can lead to several connected events. Free Spins, expanding Wilds, multipliers, cascading reels, pick features, and jackpot rounds can all change what happens after the original spin.
Starburst is a simple example of this change. Its expanding Wild can cover an entire reel and trigger a Respin.
Later games went much further, with bonus rounds that can continue for dozens of spins and multipliers that increase as the feature progresses.
What Did Megaways Change?
Megaways changed the reel layout itself by allowing the number of symbols on each reel to vary from spin to spin. This created a changing number of possible winning ways instead of a fixed set of paylines.
Big Time Gaming identifies Megaways as one of its major slot innovations.
Bonanza, released in December 2016, became one of the best-known early Megaways games. BTG currently lists the game with up to 117,649 ways to win, a 96.11% RTP, 37.94% hit frequency, a 26,000x maximum payout, cascading reactions, Free Spins, and a growing multiplier.
You can compare more Megaways slots in our dedicated guide.
How Much More Complex Are Modern Slots?
Modern slots can combine more win routes, features, prize levels, and mathematical states than early machines could physically support. The basic action of pressing spin has stayed simple while the software underneath it has become much more complex.
| Era | Representative Example | Win Structure | Major Feature |
|---|---|---|---|
| 1890s | Sittman and Pitt machine | Poker-style drum combinations | Mechanical result |
| Late 1890s | Liberty Bell | Three-reel symbol combinations | Automatic payout |
| 1960s | Money Honey | Traditional reels with electrical control | Electromechanical operation |
| 1970s onward | Early video gaming | Software-driven outcomes | Video display |
| 2000s | Mega Moolah | Reels plus progressive jackpot network | Multi-million progressive prizes |
| 2012 | Starburst | 10 paylines | Expanding Wild Respins |
| 2016 onward | Bonanza | Up to 117,649 ways | Megaways, cascades and multiplier progression |
Did Modern Slots Become Better Value Over Time?
Not necessarily. Modern slots became more complex and transparent, but more features do not automatically mean a better RTP. Player value still depends on the mathematics of the individual game.
This is an important distinction.
A modern slot may have:
- 117,649 ways to win
- Free Spins
- Growing multipliers
- Cascading symbols
- A 20,000x max win
None of those features tells you its house edge.
A simpler game can have a better RTP than a much more advanced one.
How Did the Meaning of a “Big Win” Change?
The size of possible slot prizes grew dramatically as games moved from isolated mechanical machines to software and networked jackpots. Early machines were limited by the coins and prizes they could physically hold or pay.
Modern slots can express prizes as thousands of times the stake, while progressive networks can pay millions regardless of what a physical machine could contain.
| Slot Generation | Typical Prize Model | Main Limitation |
|---|---|---|
| Early mechanical | Coins or merchandise | Physical machine |
| Electromechanical | Larger automatic coin payouts | Still tied to local hardware |
| Video slot | Complex multipliers and features | Game’s mathematical prize ceiling |
| Network progressive | Shared jackpot worth millions | Rare jackpot trigger |
Did Slots Become More Skill-Based as They Became More Complex?
No. More complicated features do not automatically give players more control over the random outcome. Modern games can offer choices inside bonuses, but the underlying slot remains a chance-based game unless a specific feature genuinely includes a skill element.
This is another unusual part of slot history.
The machines became dramatically more complicated, but the basic player action became simpler. Instead of pulling a heavy mechanical lever, a player can now tap one button on a phone.
The complexity moved from the player interface into the software.
How Did Mobile Phones Change Slot Machines?
Mobile slots changed where and how people could play rather than changing the basic idea of the slot itself. Touchscreens replaced physical buttons and games were redesigned to work on smaller screens.
Modern developers now commonly release the same title for both mobile and desktop play. For example, Big Time Gaming lists its current Megaways products for mobile and desktop platforms.
This completed a remarkable change in form. A gambling machine that once weighed many pounds and stood in a bar could now exist entirely as software inside a phone.
What Changed Most During 130 Years of Slot Machines?
The biggest change was the removal of physical limits. Mechanical reels restricted the number of symbols, combinations, features, and prizes a machine could support. Software removed most of those restrictions.
| Then | Now |
|---|---|
| Three physical reels | Variable reels, grids and changing layouts |
| Few symbol combinations | Thousands or hundreds of thousands of win routes |
| One result per pull | Cascades, Respins and long bonus sequences |
| Local fixed prize | Network jackpots worth millions |
| Mechanical payout table | RTP, volatility, hit frequency and feature information |
| Machine in one location | Software available across phones and computers |
That is the real history of slots in one table. Each technological step removed another physical restriction.
What Might the Next Generation of Slots Look Like?
The next major changes are more likely to affect presentation, personalization, interfaces, and game mechanics than the basic idea of random wagering. New technology can change how a slot looks and reacts without removing the mathematical rules required in regulated gambling.
Virtual and augmented reality may create new interfaces. Artificial intelligence may help developers build content or adapt non-mathematical parts of the experience. New mechanics will almost certainly appear.
But history suggests the most important changes will come when technology removes another restriction developers currently take for granted.
What Does the History of Slot Machines Tell Us?
Slot history is really the story of moving complexity from physical hardware into software. The earliest machines used a handful of reels and simple prizes. Electromechanical systems increased what the machine could do. Video screens removed physical reel limits. Online networks created huge progressive jackpots, and modern mechanics such as Megaways made the reel structure itself flexible.
The key stages were:
- Mechanical card and reel machines in the 1890s
- Automatic payouts through machines such as the Liberty Bell
- Mass-produced coin-operated slots
- Electromechanical machines in the 1960s
- Video gambling technology in the 1970s
- Progressive jackpot networks
- Online slots in the internet era
- Mobile slot gaming
- Modern mechanics such as Megaways, cascades, bonus buys and persistent features
The action has barely changed: place a bet and wait for a result. Almost everything underneath that action has.
Gavin has spent over a decade writing about online casinos across every major operator and market. He has hundreds of published articles about online casinos, games like slots, blackjack, and roulette, and has played at top sites across the world.