The expanding meaning in slots is simple: something on the screen grows after it lands. Usually a symbol or wild stretches to cover its whole reel, but the word can also describe a grid that adds rows. The growth itself is decided by the random outcome of the spin, not by anything you do.
Expanding means a symbol, wild or grid grows after landing, usually to fill a full reel.
Expansion is part of the spin result chosen by the random number generator, not a separate chance.
An expanding symbol on a payline slot can turn one landing into wins on many lines at once.
The game help screen explains exactly when an expansion happens and how it pays.
Term
Expanding
Applies to
Symbols, wilds, reels and grids
Common forms
Expanding wild, expanding symbol, expanding reels
Where it appears
Base game and free spins
Found in
Online video slots; rare on pub fruit machines
What expanding means on a slot machine
On a slot, expanding is a modifier word. Attach it to a symbol and it describes one picture that grows upwards and downwards until it covers every position on its reel. Attach it to a reel set or grid and it describes a playing area that gets taller or wider during a feature. The word never stands alone in a paytable; you will always see it paired with what grows.
The idea arrived with video slots. Mechanical machines described in the history of the slot machine (opens in a new tab) had fixed physical reels, so a symbol could not change size. Once reels became pictures on a screen, designers could make a symbol stretch, and expansion became one of the standard bonus features in the glossary.
Types of expanding feature in online slots
Three uses of the word cover nearly every game you will meet. They behave differently, so it pays to know which one a help screen is describing.
The main kinds of expanding feature
Feature
What grows
Typical effect
Read more
Expanding wild
A wild symbol fills its reel
Substitutes on every row of that reel, often with a respin
Expanding wilds feature page
Expanding symbol
A chosen paying symbol fills its reel
Can pay on every active line, usually in free spins
An expanding feature looks like a second event, but it is not. The random number generator picks the reel stops for the spin, and the game's rules then say what happens when a qualifying symbol is among them. If an expanding wild is in view, the software applies the expansion and evaluates the final screen. The total win was fixed the moment the outcome was drawn; the animation simply shows you how the paytable got there.
That matters because some players think the growth is a fresh roll of the dice, or that a "near" expansion was close to paying. Neither is true. The math model already counts how often expansions occur and what they pay, and that is folded into the published RTP.
Worked example: an expanding symbol on 10 paylines
Take a book-style game such as Book of Dead, which has 5 reels, 3 rows and 10 paylines. During free spins one symbol is chosen to expand. The numbers below are illustrative only, to show the mechanism; the real values are in the game's paytable.
Total stake £1, spread as 10p per line across 10 lines.
Suppose the chosen symbol pays 5 times the line bet for three of a kind.
Three of them land on reels 1, 3 and 5, one position each.
Each expands to fill its reel, so all 10 lines now carry three of the symbol.
Illustrative win: 10 lines × 10p × 5 = £5, against a single 50p line win without expansion.
In book-style games the help screen usually states that the expanded symbol can pay on reels that are not next to each other. Book of Dead is a high-volatility game with a 96.21% RTP and a 5,000x max win per its facts sheet, and its top results come from expanded symbols in free spins. That shape explains why the game can run quietly for a long stretch and then return a lot in one feature.
Expanding wilds in a low-volatility slot
Starburst from NetEnt shows a gentler use of the idea. Its wild can appear on the middle three reels, grows to fill the reel and holds in place for a respin. The game has 10 lines that pay both ways, a 96.09% RTP, low volatility and a 500x max win. Because expansions happen fairly often but pay modestly, the game spreads its return across many small wins rather than a few large ones.
Max win in pounds at common stakes (from facts sheets)
Slot
Max win
At 10p
At £1
At £2 (18–24 limit)
At £5 (25+ limit)
Starburst
500x
£50
£500
£1,000
£2,500
Book of Dead
5,000x
£500
£5,000
£10,000
£25,000
Big Bass Bonanza
2,100x
£210
£2,100
£4,200
£10,500
Max wins are rare ceilings, not targets. Over time the house edge applies to every stake, whichever feature a game uses.
UK rules that affect expanding features
Expansion itself is not regulated as a feature, but the way it is presented is. Since 31 October 2021, UK slots must not celebrate a return equal to or smaller than the stake, so an expansion that pays back 80p on a £1 spin should not trigger winning fanfare. Each spin must also last at least 2.5 seconds, and autoplay is banned, as set out in our slot game design rules explainer.
Sticky: a symbol that stays in place for later spins; expanding wilds are often sticky too.
Substitute: what a wild does when it stands in for another symbol.
Payway: the route along which an expanded symbol can form wins.
Feature: the general name for any special mechanic, expansion included.
Playing slots with expanding features in the UK
Expanding wilds and symbols turn up across most large slot lobbies, but which titles a casino carries changes often, so search the lobby for the game you want. Our two closest partner offers suit this kind of game. At Coral Casino, new players aged 18+ who deposit and bet £10 or more on slots get 100 free spins at 10p each on selected games, with 48 hours to accept them and 7 days to use them; there is no wagering on the winnings, and certain payment methods are excluded. At Ladbrokes Casino, new customers aged 18+ who deposit and spend £10 on slots get 50 free spins a day for 10 days (500 maximum), 10p each, claimed before 23:59 each day and valid for 7 days, with no wagering. Terms apply to both, and as both brands belong to the same operator you may not be able to open new accounts at each.
Coral and Ladbrokes are both run by LC International Limited (Entain). If you already hold an account with one Entain brand, you may not be able to open a new account with another; check the terms before signing up.
Significant terms: 18+. New players only. Offer runs 01/10/2026 to 01/02/2027. Deposit (certain types excluded) and bet £10+ on slot games to get 100 free spins (selected games, £0.10 each, 48 hrs to accept, valid 7 days). No wagering on free spin winnings. Deposits by Neteller, PayPal, Paysafe, Skrill, prepaid cards and certain debit cards do not qualify. Restrictions and T&Cs apply. GamCare.org.uk
Read the Coral reviewLicence: LC International Limited, UKGC account 54743. Offer checked 5 October 2026.
Significant terms: 18+. New customers only, from 14/11/25 until further notice. Certain deposit methods excluded. Deposit and spend £10+ on slots for 50 free spins a day during the first 10 days after first deposit and registration (max 500, £0.10 each, selected games, claim before 23:59 each day, valid 7 days). No wagering. Prepaid cards, PayPal, Paysafe, Neteller, Skrill and Moneybookers deposits do not qualify. Restrictions and T&Cs apply. GamCare.org.uk
Read the Ladbrokes reviewLicence: LC International Limited, UKGC account 54743. Offer checked 5 October 2026.
18+. Gambling should be entertainment that costs money, not a way to make it. Decide a budget before you play: plan a slot budget. Free, confidential help: National Gambling Helpline 0808 8020 133.
Frequently asked questions
What does expanding mean in slots?
Expanding means a symbol, wild or playing area grows after it lands. The most common example is a wild that stretches to cover every row of its reel, so it can substitute in several positions at once. Some games apply the word to a grid that adds rows during a feature instead. The game's help screen tells you which version it uses and how the result pays, and our game help screen entry explains where to find it.
Is an expanding wild the same as a stacked wild?
No, although the end result can look similar. A stacked wild lands already occupying several positions on a reel because the reel strip contains wilds placed one above another. An expanding wild lands as a single symbol and then grows. The maths can differ too: stacks depend on how the reel strip is built, while expansion is a rule applied after the stop. Compare the two on our stacked wilds page and the stacked symbol glossary entry.
Does an expanding symbol make a slot pay more?
Not overall. The slot's RTP already includes every expansion the game will produce over millions of spins, so the feature changes how wins are distributed rather than how much the game returns. Games that save much of their return for expansions in free spins tend to be more volatile, with longer quiet spells and occasional larger results. If you prefer steadier play, look at low-volatility slots and read about volatility before choosing a game.
Can I trigger an expanding wild on purpose?
No. Whether a wild lands, and whether it expands, is fixed by the random number generator when you press spin. Stake size, timing and the number of spins you have played make no difference, and online slots in Great Britain do not let you stop the reels early in any case. Our page on whether you can trick a slot machine goes through the common myths and explains why every spin is independent.
Why do book slots use an expanding symbol?
Book slots use an expanding symbol because it creates their signature moment in free spins. Before the feature starts, one symbol is picked to expand; whenever enough of it lands, it fills its reels and can pay across all lines. It gives the game a high ceiling while keeping a simple 5-reel, 10-line layout. Book of Dead and Book of Ra Deluxe both work this way. See our book slot machines guide and the book symbol page for how the scatter and expansion fit together.
Do pub fruit machines have expanding symbols?
Expansion is mainly a video slot idea. Traditional pub fruit machines rely on physical or screen reels with fixed-size symbols, and their features are built around nudges, holds and feature trails rather than symbols that grow. Some modern video-screen Category C machines borrow online-style features, so check the on-screen rules of the machine in front of you. Our fruit machine features guide and pub fruit machine guide explain what the classic features do.
What is the difference between expanding reels and Megaways?
Expanding reels add rows or positions during a feature, so the grid grows as you play through it. Megaways changes the number of symbols on each reel at random on every spin, so the number of ways to win moves up and down constantly rather than only growing. Some games combine both ideas. The Megaways slot machines guide covers the random-height system, and ways-to-win slots explains how wins are counted when the grid size changes.
Gambling can be addictive. Free, confidential help is available 24 hours a day from the National Gambling Helpline on 0808 8020 133. Visit GamCare.org.uk and GamCare, or block yourself from all UK-licensed gambling sites with GAMSTOP.
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