The main types of slot machine are classic three-reel machines, five-reel video slots, “ways to win” games, cluster-pay games, hold-and-win games, and progressive jackpot machines. They differ in how wins are formed and how the prize is built, but they share the same core: a random number generator picks the result, and the game returns a set percentage over the long run. The type tells you about the feel of play and the shape of the swings, not about a better chance of winning.
This guide describes each type, shows the arithmetic behind the ones that can be counted, and explains regional names such as fruit machines, pokies and VLTs. The mechanics are described in general terms because designs vary by maker, and the regulatory points come from New Jersey and Nevada rules. The calculations are our own.
What stays the same across every type?
Before the differences, the constants. Whatever the type, a regulated slot has these features.
- A random number generator chooses the outcome, and the display shows it. New Jersey’s slot machine approval standards say the equipment cannot make a further variable decision that changes the result after the RNG selects it.
- There is a theoretical RTP below 100%. New Jersey requires at least 83%, and Nevada’s Regulation 14.040 requires at least 75%, according to the Nevada Gaming Control Board.
- Each spin is independent. No type of slot has memory.
Everything else in this guide is a difference in presentation and in how the return is spread across prizes.
Classic three-reel slots
A classic slot has three reels and usually one payline, with symbols such as cherries, bars and sevens. The pay table is short, and you can often read it from the glass. Wins come from matching symbols on the line, and the top prize is usually three sevens or a similar rare combination.
Because the pay table is small, classic machines are the easiest to analyse. Our how slot machines work guide solves one completely. Their return comes from a few combinations, and their swings can be large, because the top prize is a rare line.
Video slots with paylines
A video slot shows its reels on a screen, typically five reels in a grid of three or four rows, with many paylines. The screen allows animations, bonus rounds and multiple themes. The bet is the line bet times the number of lines, so a 25-line game at 2 cents per line costs 50 cents a spin. Our how to read a slot pay table guide shows the arithmetic.
Video slots are the most common type. The extra screen space is used for features rather than for better odds. The design question for the maker is the same: how to divide the return between frequent small wins, bonus features and rare large prizes.
Ways-to-win slots
A “ways” game removes paylines. A win is formed by matching symbols on adjacent reels from the left, in any position on each reel. The number of ways is the number of symbol positions on each reel multiplied together.
| Layout | Ways to win |
|---|---|
| 5 reels, 3 positions each | 3 x 3 x 3 x 3 x 3 = 243 |
| 5 reels, 4 positions each | 4 x 4 x 4 x 4 x 4 = 1,024 |
| 5 reels, 5 positions each | 5 x 5 x 5 x 5 x 5 = 3,125 |
| 6 reels, 7 positions each | 7 x 7 x 7 x 7 x 7 x 7 = 117,649 |
Some ways games vary the number of positions on each reel on every spin, so the number of ways changes. The headline figure for these games is usually the maximum, reached only when every reel shows its full number of positions. Most spins have fewer ways than the maximum, and the pay table still returns the same long-run percentage.
More ways to win does not raise the return. It spreads wins across more combinations, so small wins are more frequent and each one is typically smaller.
Cluster-pay slots
A cluster-pay game uses a grid, and a win is a group of matching symbols touching each other, usually horizontally or vertically. After a win, the winning symbols often vanish and new ones drop in, which can create a chain of wins from one bet. Chains are called cascades or tumbles.
The mechanics change the feel, because several results can follow one wager. The long-run return is still set by the game’s design. A chain does not mean you won more, since the chain is counted within the same return. The excitement comes from many small payments in one spin, which fits the effect described in our guide on how gambling games hold your attention.
Hold-and-win and respin slots
In a hold-and-win game, special symbols such as coins or orbs lock in place when they land, and the game gives a limited number of respins to land more. Each locked symbol carries a prize, and filling the screen can win a jackpot.
You can see how rare the big outcomes are with a simple model. Suppose a 15-position screen lands a special symbol in each position with probability 5%. The average number of special symbols per spin is 15 x 0.05 = 0.75. The chance of at least one special symbol appearing in a spin is 1 minus 0.95 to the power 15, about 53.7%. The chance of six or more is only about 0.005%, roughly 1 in 20,000. A feature that needs a crowd of special symbols is built on a rare event.
A real game adds respins that give more chances, so the true chance of a big result is higher than this one-spin model. The point of the model is the shape: small outcomes are common and large ones are very rare.
Progressive jackpot slots
A progressive machine has a prize that grows with play until someone wins it. The jackpot can belong to one machine, a bank of machines or machines in many casinos. Part of the return is set aside for the jackpot, which usually leaves less for the small prizes. See how progressive jackpots work for the funding and the rules.
Bonus-buy slots
Some online games let you pay a multiple of your bet to start a feature straight away. The price is set so that, on average, the feature pays back a stated share of its cost. Suppose a feature naturally starts once in 150 spins and averages a payout of 90 times the bet. Buying it for 100 times the bet returns 90% of its price on average. That is a hypothetical, not a real game, but it shows that a bought feature has its own return, which may differ from the base game’s.
Rules for bonus buys differ by place, and some jurisdictions do not allow them. Check the rules of the game and the law where you play. The cost per spin when you buy features is much higher, so the average loss per hour can rise sharply.
Regional machines: fruit machines, pokies, VLTs and others
Many names refer to the same kind of device under different local rules.
- Fruit machines is the common name in the United Kingdom for slot-style gaming machines.
- Pokies is the common name in Australia and New Zealand.
- Video lottery terminals (VLTs) are machines operated within a government-run lottery system in some places.
- Penny slots is a name for low-denomination games. As the pay table guide explains, the cost per spin can be far more than a penny.
- Sweepstakes slots are games offered under a sweepstakes model with virtual currencies, and their legal status differs by place.
Local law decides which of these exist, what they can pay and how they are regulated. See is gambling legal where you live.
How do you choose between types?
The type changes the experience, and the numbers that decide your cost are the same for all of them.
| If you prefer | Look at | What to check |
|---|---|---|
| Simple play | Classic three-reel | Top prize relative to the bet |
| Lots of features | Video slots, hold and win | Total bet and cost of buying features |
| Frequent small wins | Ways and cluster games | The size of typical wins against the bet |
| A chance at a very large prize | Progressives | The share of return set aside for the jackpot |
Our how to choose a slot guide explains how RTP, hit frequency and volatility fit together, whichever type you pick.
What does it cost to play any type?
Every type costs the total wager times one minus the RTP. At 600 spins an hour and a $1 bet, you wager $600 an hour, and at 83% the average cost is $102. A different type of machine does not change this. Set your budget and time before you start and stop when you reach it. Our guide to setting a gambling budget and time limit shows how, and the Safer play toolkit lists tools and support. If gambling is causing harm, visit our get help page.
Where should you go next?
For the core mechanics, read how slot machines work. To learn the vocabulary behind these types, see the slot machine terms glossary. And to see what regulators require, read are slot machines rigged.