Slot Reels: Types and Mechanics Explained
You press spin, watch the reels turn and wait for the symbols to stop. A big win can bring a joyful shout; a loss may draw a sigh. For many people trying the latest online casino slots, that mix of anticipation and emotion is part of the experience.
But what goes on inside a slot machine? The on-screen result depends on several connected elements. The maths model, RNG (random number generator) algorithm, RTP, variance or volatility, and reel mechanics all influence how the game looks and plays, as well as the outcome it produces.
Many of these terms will be familiar, since they come up repeatedly in slot coverage. We also have guides to RNG and RTP and variance. The reels themselves are easier to overlook: they are the rotating parts that display symbols during a spin. This guide focuses on slot reels and the mechanics behind them.
Slot games use a variety of reel layouts and counts. Traditional machines generally had 3 reels and one payline, while other games feature 5, 6, 7 or many more reels, with some offering 100,000+ ways to win. Some modern titles do not use conventional reels at all.
Slot Reel Basics
The earliest slot machines had only a few reels. Each mechanical reel turned, and a payout was awarded when the reels stopped with the required matching symbols on the single payline. The prize depended on the winning combination.
Many modern slots still use reels to generate results, but the format has grown well beyond three reels. Games with at least 5 reels are common, and some online or digital titles describe their reel count as infinite because the layout can keep expanding.
Reels can form winning combinations, but modern games often include bonus symbols too. Scatter symbols may trigger free spins, bonus games or other features, while Wild symbols usually substitute for regular symbols to complete combinations on active paylines.
Three-Reel Slots
When slot machines first became popular, they generally had 3 reels. Most offered one payline, or at most 3, and a spin showing 3 matching symbols across a line won a prize. The amount depended on the symbols that appeared.
Developers still release 3-reel games today, including titles with as many as nine reels. These are usually classic or retro slots designed to recall machines from an earlier era. Compared with modern video slots, they tend to have fewer paylines and bonus features.
Some 3-reel online slots to consider:
Five-Reel Slot Machines
Whether you play at an online casino or a land-based venue, there is a good chance the game has five reels. The most familiar layout is 5x3: 5 reels arranged across 3 rows.
Although this layout is widespread, developers set their 5-reel releases apart with their presentation and features. The best slots may combine striking graphics with bonus features such as free spins and mini-games, and some may also offer progressive jackpots.
Extra reels can make room for more paylines. Available formats include 5-reel slots with 10, 20, 30, 40 or 50 paylines, as well as games with even more. Depending on the reel mechanics, some titles use thousands or even hundreds of thousands of ways to win.
Some 5-reel slots to explore:
Seven-Reel Slots
While 5-reel slots are still the norm, that format faces growing competition. Games with seven or more reels are now commonplace. Many depart from conventional paylines, using alternatives such as Cluster Pays or Megaways. A later section of this guide to slot reels, machines and mechanics explores these systems and their associated features in detail.
Games with many reels often include several bonus rounds and extra features. Depending on the title, you might find cascading reels, horizontal reels above or below the main reels, and other variations.
Popular 7-reel slots include:
Ten-Reel Slots
Games now come with x, y or z reels, and some let you unlock extra reels during play. More reels generally allow more possible paylines, so a 10-reel slot with only 3 paylines would be unusual. Open a 10-reel slot’s paytable and you may see a long list of payouts for numerous symbol combinations.
Some games with 10 reels:
Infinireels and Infinity Reels
Modern reel designs are varied, and some games can potentially keep adding reels without a stated limit.
Infinireels and Infinity Reels are two well-known examples. NetEnt developed Infinireels, while ReelPlay created Infinity Reels. Both start with three reels. When a winning combination lands, another reel is added and the game awards a re-spin. Each subsequent win adds a reel, and the process continues while the relevant conditions are met. In theory, it could go on indefinitely, hence the names Infinireels and Infinity Reels.
Infinireels and Infinity Reels slots available at online casinos:
Slot Games with Megaways
Reel count is not the only way modern slots generate wins. Some use alternatives to traditional paylines, including the Megaways mechanic developed by Big Time Gaming. This system works differently from a fixed-payline game.
Many titles use the word 'Megaways' because Big Time Gaming licensed the popular mechanic to other software providers. Rather than matching symbols along fixed paylines, players need matching symbols in any position on consecutive reels. This resembles the approach used by Ways-to-Win games.
The key difference is the number of symbols that can appear on each reel. Ways-to-Win uses a fixed number, while Megaways uses a random reel modifier that can display between 2 and 7 symbols on each reel. The number of available 'paylines'—more accurately called 'Ways-to-Win'—therefore changes with every spin. One result might offer 100 ways; another could provide thousands. Some games can reach 117,649.
Megaways slots to consider:
Video Slots Without Reels (Cluster Pays No-Reel Slots)
Some casino slots have no reels and look more like mobile puzzle games such as Candy Crush. Features can still keep the action moving, with multiple wins possible from one spin. Free-spin rounds, Wild symbols, bonus-wheel symbols, multipliers and other additions may be included. The main difference is how winning combinations form and pay out.
In Cluster Pays slots, matching symbols must form connected groups, usually of 5 or more symbols joined vertically or horizontally. Many also feature avalanche reels: winning symbols disappear from the 'reels', and replacement symbols drop into the gaps. The new layout may form further wins, repeating the sequence.
Popular Cluster Pays slot games include:
Reel Slots vs. Slots Without Reels (Our Opinion)
How do games without reels compare with traditional reel slots, and is one format better? It comes down to personal preference, though the variety available today is a plus. This opinion draws on reviews of thousands of slots over the years; the comparison below reflects that perspective.
Cluster Pays games, which technically have no reels, often feel more active. A single spin can set off several chain-reaction wins, and these games often have a wide range of bonuses. The ongoing movement can give the impression that something is always happening.
That does not automatically make Cluster Pays better than reel-based games. Many 3-reel, 5-reel, 7-reel and 10-reel slots have appealing features too. Their structure is often more restrained, with one main bonus feature supported by elements such as Wilds and Scatters.
