Reels are the vertical columns of symbols that spin on a slot machine and stop to show the result. Most online slots use five reels with three rows of symbols, but layouts range from three reels to six-reel Megaways grids. On a modern slot, a random number generator decides where the reels stop before they appear to land.
A reel is one vertical column of symbols; the grid is reels across by rows down.
Online, a random number generator picks the stopping positions; the spin animation only shows the result.
With 'ways to win', a 5x3 grid gives 3 x 3 x 3 x 3 x 3 = 243 ways; six reels of seven symbols give 117,649.
The Gambling Commission defines an online slot as a reel-based casino game, so the £5 and £2 stake limits apply.
Meaning
Vertical columns of slot symbols
Most common online layout
5 reels × 3 rows
Liberty Bell (Charles Fey)
3 reels, 5 symbols
243 ways
5 reels of 3 symbols
Megaways maximum on 6 reels of 7
117,649 ways
UK minimum spin time
2.5 seconds (online slots)
What slot reels are
Each reel is a strip of symbols arranged in a column. When you press spin, every reel turns and then stops, and the symbols left in view form a grid. Wins are read from that grid using the game's rules: paylines, ways to win, clusters or scatter pays. The number of reels and rows is called the layout, written as reels × rows, so '5x3' means five reels each showing three symbols.
This glossary entry covers where reels came from, how they work inside an online slot, the main layouts you'll meet in our slot reviews, and the UK rules that mention them.
From mechanical reels to virtual reels
The best-known early slot, Charles Fey's Liberty Bell, had three reels and five symbols: horseshoes, diamonds, spades, hearts and a Liberty Bell, with three bells paying the top prize. The Wikipedia slot machine article (opens in a new tab) dates it to some time between 1887 and 1895, while its article on Fey gives 1898. Physical reels limited the number of stops, and so the size of the top prize.
In 1984 the Norwegian mathematician Inge Telnaes received a US patent for using a random number generator to choose reel stops. With virtual reels, each reel can have many more 'stops' than the physical strip shows: 256 virtual stops on each of three reels give 256 × 256 × 256 = 16,777,216 combinations. Our history of slot machines covers the full story, and the classic 3-reel slots page covers games that keep the old look.
How reels work in an online slot
Online, the reels are pictures. When you press spin, the game's random number generator picks the result, and the reels animate to show it. Stopping the reels early couldn't change the outcome, and in Great Britain it isn't allowed anyway: slam stop and turbo features are banned under RTS 14E. The Gambling Commission's RTS 7 rules on random outcomes (opens in a new tab) also ban designs that mislead you about your chances, including swapping losing results for near misses.
A near miss, with two jackpot symbols and the third just above the line, is not a sign that a win is close. Each spin is independent. See can a slot be due a win?
With ways to win, matching symbols on adjacent reels from the left pay, wherever they sit on each reel. The count is the number of rows on each reel multiplied together: 5 reels of 3 rows give 3 × 3 × 3 × 3 × 3 = 243 ways, and 5 reels of 4 rows give 1,024. Megaways changes the number of symbols on each reel every spin. Six reels showing the maximum seven symbols each give 7 × 7 × 7 × 7 × 7 × 7 = 117,649 ways, but a spin with fewer symbols has fewer ways.
Do more reels mean better odds?
No. More reels or more ways change how often small wins land and how the prizes are spread, but the game's RTP is set by its maths, not its layout. Starburst, with 10 paylines, has an RTP of 96.09%, and Bonanza Megaways, with up to 117,649 ways, has 96.00%. At £1 a spin, both cost about £4 per 100 spins on average. Volatility, not the reel count, decides how bumpy the ride feels.
Reels and UK slot rules
The Gambling Commission's online slots stake limit guidance (opens in a new tab) defines an online slot as a casino game using a reel format played over the internet. That definition is why the £5 per spin limit for adults aged 25 and over (from 9 April 2025) and the £2 limit for 18 to 24-year-olds (from 21 May 2025) apply to reel games but not to roulette or blackjack. Every spin must also take at least 2.5 seconds. See slot stake limits and game design rules.
These are slot offers, so they fit reel games better than most of our glossary topics. Check which games each offer covers in the terms, and remember the house edge still applies while you play. 18+ and terms apply.
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Frequently asked questions
What are reels on a slot machine?
Reels are the vertical columns of symbols that spin and stop to show each result. A 5x3 slot has five reels, each showing three symbols, which together make the grid that wins are read from. Online the reels are animations, and a random number generator picks where they stop. Our slots hub reviews games with every common layout.
How many reels does a slot have?
Most online slots have five reels, but three-reel classics and six-reel games are common. Megaways games such as Bonanza Megaways use six reels with two to seven symbols each, and grid games like Reactoonz use a 7 × 7 layout without traditional reels. The layout is listed in each game's help screen. See our Megaways guide for variable reels.
Are slot reels random?
Yes. On a UK-licensed online slot, a random number generator picks the result, and the Gambling Commission's technical standards require the output to be acceptably random and tested. The reels' spin and stop only show what was already decided. Patterns and timing make no difference. Our page on random number generators explains how this is checked.
Do more reels mean a bigger chance of winning?
Not in the sense of better value. More reels or ways can mean more frequent small wins, but RTP is set by the game's maths, not by its layout. Starburst's 10 paylines return 96.09% and Bonanza Megaways' 117,649 ways return 96.00%. Volatility describes how wins are spread. Read our RTP guide for what the figure means.
What does 5x3 mean on a slot?
5x3 means five reels across and three rows down, so 15 symbols are visible after each spin. It is the most common online layout, used by Starburst, Book of Dead and Gonzo's Quest. On a ways-to-win game, a 5x3 grid gives 243 ways (3 multiplied by itself five times). Our paylines guide explains the alternative.
Can you stop the reels early on UK slots?
No. Since 31 October 2021, UK online slots can't offer slam stop, turbo or quick spin, and each spin must last at least 2.5 seconds. Stopping the reels would never have changed the result anyway, because it is decided when you press spin. Our page on game design rules lists the full set of UK slot rules.
What are virtual reels?
Virtual reels are the number-based reels a random number generator uses to choose stops, rather than the physical strip you see. Inge Telnaes patented the idea in the US in 1984. With 256 virtual stops on each of three reels, there are 16,777,216 combinations, which allows bigger top prizes. See our history of slot machines.
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