Expanding wilds slots

What expanding wilds are in online slots

A standard wild symbol covers one position. This kind of wild covers one position for a split second, then stretches up and down until every row of its reel is wild. On a 5×3 grid that turns one wild into three; on a 6-row grid it turns one into six.

The idea only became practical with video slot machines. A physical reel can only show what is printed on its strip, but a screen can redraw a reel however the game rules say. That is why expanding wilds are a staple of five-reel video slots and have no direct equivalent on a mechanical three-reel machine.

The glossary entry for expanding covers the general term. On this page the focus is wilds that expand, which is a narrower and more powerful thing than an expanding paying symbol.

Why a full wild reel touches every payline

Every payline is a path that visits each reel exactly once, choosing one row on each. So whichever row a line uses on reel 3, a fully wild reel 3 has a wild there. On a 10-line game, one expanded wild on any reel sits on all 10 lines. On a 243 ways game the same logic applies to every way.

The last row is the key one. With reels 2, 3 and 4 fully wild, every line automatically carries four of a kind of whatever symbol sits on reel 1 at that row. If the game pays both ways, lines are also counted from reel 5 leftwards, so the right-hand symbol scores too. That is the heart of the Starburst design.

How an expanding wild is triggered and resolved

Nothing about the expansion is decided after the reels stop. The random number generator picks reel stops, and the result already contains the wild. The animation of it growing is a display of a rule that is applied before any win is counted.

1. You start the spin at your chosen stake; the RNG selects a stop on each virtual reel.
2. If a wild is among the visible positions on a reel where wilds may expand, the rule marks every position on that reel as wild.
3. Some games then lock the wild reel and award a respin; others simply pay the spin.
4. Wins are evaluated across all paylines or ways, with the wild reel substituting on each.
5. If a respin was awarded, the locked reel stays and the other reels spin again; new wilds can expand and add further respins.
6. When no new wild arrives (or the respin limit is reached), the reels clear for the next paid spin.

Step 3 is where designs differ most. In Starburst, each expanding wild on reels 2, 3 or 4 locks and gives a free respin, so a run can last up to three respins if all three middle reels end up wild. Other slots skip the respin and attach a multiplier or a symbol upgrade instead.

Expanding wilds vs expanding symbols

The two are often confused because both fill a reel. The difference is what they become.

• Expanding wild: the reel becomes wild, so it substitutes for whatever symbols the other reels show. It helps every line equally.
• Expanding symbol: a chosen paying symbol fills its reel, usually only in free spins, and then pays as if it were on every line (often even on non-adjacent reels). It helps only that one symbol.
• In Book of Dead and other book slots, the book is wild and scatter, but the expanding element is a separate special symbol chosen at the start of free spins.
• Our expanding symbols guide covers that second mechanic in full.

Popular expanding wilds slots in the UK

These slots use expanding wilds as a main feature. Figures are from our verified specification data; casinos can run lower-RTP versions, so check the help screen of the game in front of you.

The spread is striking. Starburst uses expanding wilds to produce frequent, modest wins: low volatility and a 500x ceiling. Starburst XXXtreme keeps the look but adds multipliers to the wild reels, and its listed maximum jumps to 200,000x. Same core feature, completely different risk.

Eye of Horus shows another use: the expanding Horus wild in free spins also upgrades lower symbols, so the grid improves as the round continues. Hacksaw Gaming’s Fist of Destruction (opens in a new tab) and Red Tiger’s Trillionaire Megaways (opens in a new tab) build their main features around expanding wilds, the latter combining them with multipliers on a Megaways layout.

A related shape is the fixed oversized wild. Starburst Galaxy (opens in a new tab), for example, places a 3×3 Starburst wild on an expanded 7×7 grid rather than growing a single reel.

How expanding wilds change the maths

Reel-filling wilds are a cheap way for a designer to create lots of small wins: one landed symbol becomes several, and every line benefits. The cost is paid elsewhere. To keep the same RTP, symbol pays are trimmed and wild frequency is controlled through the reel strips.

Where the expanding wild has no multiplier, the result is usually lower volatility: wins arrive often, but no single combination can be enormous because the wild only substitutes. That is Starburst’s profile. Once multipliers are attached, the same feature can drive very high volatility, because three expanded reels each carrying a multiplier can stack into a large total.

The general rule: the expansion decides how often a spin pays; anything attached to the expanded reel (multipliers, upgrades, respins) decides how big the rare outcomes get. Reading both halves in the paytable tells you more than the feature name does.

What expanding wilds slots cost per hour

UK online slots must take at least 2.5 seconds per spin, so the absolute maximum is 1,440 spins an hour. Most people play slower, but the ceiling gives a useful upper bound. At a 96% RTP, the average cost is 4% of everything staked.

Low-volatility expanding wilds slots keep returning small amounts, which can make a balance last longer than expected, but the arithmetic still runs one way over time. Our cost per hour guide shows how to adjust for slower play.

Expanding wild myths

• ‘Two expanding wilds in a row means a third is coming.’ Each spin or respin is drawn fresh. A run of wilds says nothing about the next draw.
• ‘Low stakes stop the wilds expanding.’ In most modern online slots the feature rules are identical at every stake and only the cash value of wins scales; the help screen would say if a game worked differently.
• ‘The respin is a second free chance that costs nothing.’ It costs nothing extra on the spin, but its value is already counted inside the RTP you are paying for.
• ‘Stopping the reels early catches the wild.’ UK slots can’t offer slam-stop, and in any case the result is fixed before the reels stop.

Is there a fruit machine version of expanding wilds?

Not in the classic sense. A traditional pub fruit machine relies on physical or simulated reels, holds, nudges and a feature board, and its symbols are what they are. Modern Category C machines (£1 maximum stake, £100 maximum prize, 18+) often run video games that borrow online mechanics, so you may see wild features on their screens, but the reel-filling wild is fundamentally a video slot idea.

Whatever the cabinet, the same truth holds: a machine’s long-run return is set by its design, and no feature, held reel or well-timed nudge changes that built-in percentage.

UK rules for expanding wilds slots

The Gambling Commission’s online slot design rules (opens in a new tab), in force since 31 October 2021, apply to every expanding wilds slot offered in Britain.

• No autoplay, turbo or slam-stop; at least 2.5 seconds per game cycle (spin speed rule).
• A respin win that returns your stake or less must not be celebrated with win sounds or graphics.
• Your balance and net position must be visible throughout the session.
• Maximum stake per spin: £5 if you are 25 or over, £2 if you are 18–24 (online slot stake limits).
• No feature buy in slots supplied to Great Britain, and demo play only after age verification.

Where to play expanding wilds slots

Our partner casinos list slots from many of the studios above, but lobbies change, so search for the title you want rather than assuming it is there. Each offer is for new customers aged 18+, and terms apply.

• Coral Casino: bet £10 on slots, get 100 free spins (10p each on selected games, accept within 48 hours, use within 7 days, no wagering on winnings). Runs 1 October 2026 to 1 February 2027; e-wallets, prepaid cards and certain debit cards don’t qualify.
• Ladbrokes Casino: play £10 on slots, get up to 500 free spins as 50 a day for 10 days (10p each, selected games, claim by 23:59 daily, 7-day validity, no wagering). PayPal, Paysafe, prepaid cards and some e-wallets are excluded.
• PlayOJO: 80 no-wagering free spins on Big Bass Bonanza (10p each) with a first deposit of £10 or more; winnings paid as cash. Not available in Northern Ireland.

Coral and Ladbrokes share an operator (LC International Limited, part of Entain), so read the terms on holding accounts with both. If you want help with your gambling, GamCare (opens in a new tab) runs the free National Gambling Helpline on 0808 8020 133.

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.