Expanding Symbols in Slots: How Expanding Wilds and Full-Reel Symbols Work
An Expanding Symbol lands in one spot, then grows to cover more of the reel or grid it’s already on. Nothing gets added to the screen. The symbol just takes up more of it.
A Wild stretching down a whole reel, as in Starburst, is the familiar version. But in Book of Dead the symbol that grows is a regular one, chosen for Free Spins.
What are Expanding Symbols?
A symbol lands small, then the game’s rules allow it to occupy extra positions. Those positions were already on the screen. Expansion changes the symbol’s footprint, not the size of the reel or grid.
How do Expanding Symbols work?
In Starburst, a Wild landing on reel 2, 3 or 4 expands over that reel and substitutes for the paying symbols. Book of Dead works differently: it picks a regular pay symbol for Free Spins, and the chosen symbol only expands when that adds a prize on the active paylines.
Both can end with a full reel covered by one symbol, but the reason it happens is different. In one game an eligible Wild expands on landing; in the other, selection and a win condition come first.
It isn’t only a bonus-round thing, either. Starburst expands its Wilds in the base game, Eye of Horus does it in the base game and Free Games, and Katmandu Gold’s Expanding Win works outside its bonus. The Book-style games here keep their expanding symbols for Free Spins.
Pick any two games in the Face-Off to compare how their symbols expand.
Compare how two slots use Expanding Symbols
Choose two games to see what activates an expanding symbol, how it spreads and the rules that make each feature different.
At a glance
| Starburst | Rich Wilde and the Book of Dead | |
|---|---|---|
| What triggers expansion | A Starburst Wild lands on one of the middle three reels: 2, 3 or 4. | In Free Spins, after normal wins are counted, copies of the selected symbol expand only if that adds prizes on active paylines. |
| How the symbol expands | The Wild expands to fill its entire reel and substitutes for paying symbols. | Qualifying copies fill all three positions of their reels; they do not have to be adjacent. |
| Key rule or exception | The expanded Wild triggers a respin and stays in place while the other reels spin again. It clears when the respins end. | One ordinary symbol is picked at random before Free Spins and stays the same until they end. |
Explore the expanding-symbol rules
An expanding symbol spreads across positions already on the screen. It might fill a reel, replace symbols along an arrow or grow into a larger Wild. That is different from Expanding Reels, where the playable grid itself gains positions. The trigger, qualifying conditions and follow-on rules vary from game to game.
Starburst
Expanding-symbol featureExpanding Starburst WildBase game
- What triggers expansion
- A Starburst Wild lands on one of the middle three reels: 2, 3 or 4.
- How the symbol expands
- The Wild expands to fill its entire reel and substitutes for paying symbols.
- Key rule or exception
- The expanded Wild triggers a respin and stays in place while the other reels spin again. It clears when the respins end.
Sources: NetEnt OpenBet Game Sheet v1.2
Rich Wilde and the Book of Dead
Expanding-symbol featureSpecial Expanding SymbolFree Spins
- What triggers expansion
- In Free Spins, after normal wins are counted, copies of the selected symbol expand only if that adds prizes on active paylines.
- How the symbol expands
- Qualifying copies fill all three positions of their reels; they do not have to be adjacent.
- Key rule or exception
- One ordinary symbol is picked at random before Free Spins and stays the same until they end.
Sources: Play'n GO Rules and Settings GRS0595
Are Expanding Symbols always Wilds?
No. Starburst and Eye of Horus, a very popular game you’ll find in nearly every UK lobby, use Expanding Wilds. In the version I checked, the Horus Wild grows into a stack on reels 2, 3 or 4.
Book of Dead and Pyramid King pick a regular symbol for Free Spins instead, and in Pyramid King it expands when there are enough of it for a win. A symbol can grow without being a Wild, and a Wild doesn’t have to expand.
Do Expanding Symbols always fill a reel?
Not all of them. Two games here grow in quite different shapes.
In King Frog Feast‘s Free Games, the King Frog Wild grows from one square to a 2×2 block if it eats four or more bugs in a spin. That’s as big as it gets, and it can shrink back to one square on the next spin if it doesn’t eat enough.
In Katmandu Gold, a winning symbol with an Expanding Win arrow grows in the direction the arrow points, taking over eligible symbols in its path. Some symbol classes are protected and stay put.
| Game | Symbol | Shape | What sets it off |
|---|---|---|---|
 Starburst |
Wild | Full reel | Lands on reel 2, 3 or 4 |
 Rich Wilde and the Book of Dead |
Selected regular symbol | Full reel | Free Spins, when it adds a prize |
 King Frog Feast |
Wild | 2×2 at most | Free Games, after eating four or more bugs in a spin |
 Katmandu Gold |
Winning symbol with an arrow | Along the arrow | Expanding Win |
How Book-style expanding symbols differ
Book of Dead picks one regular symbol for Free Spins. Once the normal line wins are counted, that symbol can spread over its whole reel, but only if doing so adds a prize on the active paylines. The expanded symbols then pay even if their reels aren’t next to each other, which is a Book of Dead rule rather than something every expanding symbol does.
Legacy of Dead starts with a chosen symbol too, but Free Spins retriggers add more expanding-symbol types to the same feature. In Book of Hidden Tombs, the chosen Golden Expanding symbol needs a different number of matches depending on which symbol it is, and when it qualifies, its full-reel expansion is evaluated across 10 lines.
Same idea, three different sets of rules.
Expansion alongside other features
Starburst makes the difference between expansion and persistence easy to see. First a Wild expands across its reel. The Wild then stays held during the respin sequence. That second part is Sticky Wild behaviour, not what makes the symbol expand.
In Eye of Horus Free Games, the expanding Wild also activates symbol upgrades. Battle The Beast goes further. When a Bear Wild and a Viking Scatter land on neighbouring reels, both expand and then fight it out, and the winner takes over the reels involved. Expansion is only one stage in those features.
Not the same as Giant Symbols or Expanding Reels
A Giant or Colossal Symbol can land already covering several positions. An Expanding Symbol begins smaller and grows after landing or activation. King Frog Feast’s Wild is a good example: it starts as one square and only becomes 2×2 later. A large symbol on the screen doesn’t, by itself, tell you which process happened.
Expanding Reels
Expanding Reels add playable positions, while expanding symbols use the ones already there. Katmandu Gold has both: Expanding Win makes a symbol bigger, while its Avalanche can add rows to the grid.
Expanding Symbols FAQ
Is an Expanding Wild the same as an Expanding Symbol?
An Expanding Wild is one kind. Starburst’s Wild fills its reel and Eye of Horus’s grows into a stack, but in Book of Dead the symbol that expands is a regular one.
Do expanding symbols make wins more likely?
Not on their own. Expansion changes how much space a symbol covers, not the game’s RTP, volatility or how often it pays.
Sources reviewed
I checked these games against their own rules, developer material and game pages. Some evidence is only available in-game or through authenticated sources; the public links identify the games.
NetEnt
Play’n GO
Blueprint Gaming
ELK Studios
Habanero
Pragmatic Play
BGaming
Where this guide comes from
I check each game’s own rules for which symbols can expand, what sets them off, how far they grow and whether they stay. Where a rule belongs to one game, I say so. Read the full research methodology