Types of Slot Machines: From Single-Line Games to Progressive Jackpots
Slot machines have grown from the familiar three-reel cabinets in land-based casinos into a wide range of games for both in-person and online play. Modern versions may feature elaborate themes, multiple paylines, bonus rounds, and many ways to win. This guide covers the main slot machine types, setting out their defining mechanics and how they differ. Whether you play on a casino floor or browse online, you can find formats with distinct features and styles.
Old-School Classics
Some players prefer a simpler style. These three-reel, single-payline machines keep their vintage look and uncomplicated gameplay, bringing a nostalgic feel to brick-and-mortar venues and popular online casinos. Familiar cherry and lemon symbols evoke gambling machines once nicknamed one-armed bandits. While newer games compete with vivid graphics and layered features, classic slots keep things simple.
Traditional three-reel slot machines remain fairly popular, though they now share the market with many other slot formats. The rest of this guide introduces those alternatives and explains what sets them apart.
Classic Slots with Modern Features
Players looking for more than one payline can try Classic Slots with three reels and a range of contemporary features. Scatter-triggered free spins, multiple paylines and other extras pair the familiar classic format with mechanics found in newer games.
3-reel slots with modern features:
Modern Video Slot Games
Traditional machines still have plenty of fans, but many players prefer to play modern video slots for their bonus features, special symbols, jackpots and inventive reel mechanics. Most online slots now have five reels, while others feature extra reels, Cluster Pays or Megaways mechanics. The sections below outline the main types of modern video slots.
Multi-line Slot Machines: More Ways to Win
Early fruit machines with a single payline could frustrate players when a symbol came close to completing a jackpot combination. Multi-line slots offer 50, and sometimes more than 100, possible line patterns, including zigzags and diagonals across the reels. With more lines, a spin has more ways for matching symbols to form a winning combination.
- Adjustable Payline Slots: Some earlier BetSoft multi-line online slots, such as A Night in Paris and Greedy Goblines, allow players to choose how many lines are active on each turn. Playing with the maximum number can add to the action. The original Rich Wilde and the Book of Dead also lets players adjust the paylines from 1 to 10 and choose how many coins to play.
- Fixed Payline Slots: Software providers generally no longer offer adjustable paylines as a feature in video slots. As a result, most new online slots have fixed paylines instead of letting players choose the number of lines.
Mobile Video Slots
Mobile slots are sometimes treated as a separate category, but virtually every online slot is now designed for mobile phones. Video slots are also found in land-based casinos. For example, Book of Dead is available as a mobile slot at Play'n GO online casinos and as a video slot in William Hill land-based betting shops.
HTML5 development enables smooth play on desktop computers, phones and tablets. Players can tap to spin wherever a data connection is available. Touchscreen layouts adapt controls for smaller displays, while online-only mobile casinos can offer hundreds of modern video slots without downloads or physical machines. This makes a quick game easy to access when the urge to play strikes.
Cascading Reels: Multiple Wins in One Spin
In cascading-reel slots, symbols disappear after forming a winning combination, and the symbols above drop into the empty spaces. New symbols arrive from the top, giving the same spin another chance to form a winning combination and start a chain of consecutive wins.
Red Tiger Gaming’s Rainbow Riches Drops was among the early games that helped popularize cascading reels. Other titles followed, including the well-known Gonzo's Quest, which offers several chances to win during a spin.
Some top picks among slots with cascading reels:
Cluster Pays: Wins from Symbol Clusters
Instead of using traditional paylines, Cluster Pays slot machines award wins when matching symbols form a cluster. In many games, a cluster needs at least 5 symbols anywhere on the grid, but the exact requirement varies, so check the paytable.
- The popular Reactoonz slot machine by Play'n GO takes the Cluster Pays format further with
- a 7x7 grid and exciting bonus features.
- Other notable games include NetEnt's Aloha! Cluster Pays
- Cluster Pays and the unusual Wanted Dead or a Wild by Hacksaw Gaming
Cluster Pays video slots take a different approach to slot play: wins come from groups of matching symbols rather than set paylines.
Megaways Slot Machines
Slot developers keep experimenting with new mechanics. One influential format is Megaways™ slots, created by Big Time Gaming. These games change the number of symbol positions on each reel from spin to spin and can offer up to 117,649 winning combinations.
Bonanza by Big Time Gaming and Gonzo's Quest Megaways™ from NetEnt are well-known examples. Some games also blend formats, such as multi-line progressive jackpots or classic three-reel and five-reel machines with multipliers.
Explore several slots featuring the Megaways mechanic below:
Bonus Multiplier Slots
Like straightforward multiplier games, Bonus Multiplier Slots calculate wins based on the number of coins wagered. The source discussion also states that larger coin bets can unlock bonus payouts and bigger jackpots unavailable at lower wagers. It therefore presents maximum-coin play as a way to access greater potential rewards, while noting that experts are said to favour minimum bets because top prizes are rare. These points describe the game structure and an opinion about bet sizing, not a guarantee of results.
Combination Slots
Combination Slots bring together features from two or more slot categories. A familiar example pairs multi-line play with a progressive jackpot, combining two distinct features in one game. Other combinations may include classic three-reel slots with multipliers or bonus multiplier games with cascading symbols. Blending formats gives developers more ways to shape the playing experience.
Megaspin Slots
Megaspin Slots feature several sets of reels that can spin at once. A game may have three to five sets, or as many as nine, creating a much larger visual layout. Multiple reel sets are commonly activated at random during free spins or bonus rounds.
Infinity Reels
Infinity Reels and Infinireels are associated with the Yggdrasil and NetEnt software providers. Partner networks on the Yggdrasil Masters platform, including Relax Gaming, Bang Bang, Reel Play and 4thePlayer, also feature the mechanic in online slots. A win can repeatedly add reels to the game, with no stated limit—hence the reference to infinity.
Progressive Jackpot Slots
The chance to win a large progressive slots jackpot is a major draw of this category. When games are linked across machines, a small portion of each bet can go towards a shared prize pool that grows over time. The progressive jackpot is shared across a network, with players on different machines contributing to the same pool. A large displayed prize does not make a win likely or certain.
Progressive prizes can reach exceptional amounts. In 2013, a Finnish player reportedly won nearly €18 million in a single spin on the Mega Fortune progressive jackpot slot machine network. The source also records numerous later jackpot wins at different casinos, including a world-record €38.5 million payout on one of the WowPot progressive slots in 2023.
Top networks with large progressive jackpots:
- Mega Moolah (Games Global)
- WowPot (Games Global)
- Jackpot King (Blueprint)
- Dream Drops (Relax Gaming)
- Age of the Gods (Playtech)
These titles may be offered together at one casino or distributed across several operators. One casino featuring Mega Moolah, WowPot, Jackpot King, Age of the Gods and Dream Drops is LeoVegas.
Non-Progressive Slot Machines
Fixed-jackpot slots are another format found at multiple casinos. Their prizes typically do not reach the amounts associated with progressive games, but they can still pay substantial wins. Instead of growing as bets contribute to a network, the jackpot stays fixed up to a stated maximum.
New Online Slot Machine Innovations
Slot development keeps changing as iGaming studios find new ways to shape their games. The mechanics outlined above are only part of the picture; other innovations were also drawing attention in the slot market during the period discussed.
For instance, Yggdrasil has created engagement mechanics that change reel behaviour, add special symbols or introduce extra symbols during a bonus round. These systems give individual games a more distinctive structure.
See what Yggdrasil has introduced in recent years:
- TopHit - An extra "top hit" reel turns fully visible high-paying symbols into wilds when they land and can also trigger multipliers.
- Gigablox - Several symbol positions can merge into one large block that may deliver substantial wins.
- Multimax - Wins can be multiplied up to 10x during a bonus round or bonus game.
- Splitz - Reels split into independent reels with up to 10,000 bet ways.
- Gagarise - Losing spins can become winning spins when high-paying symbols turn into wilds.
- Doublemax - A mystery-symbol mechanic can double scatter pays.
- Wild Fight - Wild symbols battle one another, with more fights associated with larger payouts.
- Duomax - Two chance-based mechanics, Respins and Upgrades, offer multiple opportunities to win.
- Fastpots - Quick mini jackpots build from bets and can then trigger payouts.
- Wildenergy - A collector mechanic uses special symbols to unlock Energized Wilds that may lead to large wins.
Yggdrasil is not the only software provider introducing new mechanics across multiple platforms. NetEnt drew on Evolution and its XXXtreme gameplay from Live Casino in developing related video slot concepts, while BGaming was described as having recently launched MergeUp. This mechanic lets clusters merge and upgrade into high-paying symbols. These examples reflect broader experimentation among developers in recent years.
