Expanding Reels Slots: How Reel and Grid Expansion Works
Expanding Reels have come a long way. What started as a fairly simple idea, making a reel taller or adding a few positions, has developed into some quite elaborate features.
Vikings jumps from a 5×3 grid to 7×5 during Raid Spins. Cowboy Coins grows individual reels, while Folsom Prison gradually unlocks positions on a larger grid. Same basic idea, but three very different ways of doing it.
What are Expanding Reels?
An Expanding Reels game starts with a smaller active playing area and opens up more positions when something specific happens. That’s different from a Wild stretching across spaces that are already there, or Megaways reels that change height every spin anyway.
How do Expanding Reels work?
Most examples are a simple before and after. The game starts with a smaller active layout, something triggers the change, and the new layout has more playable positions. It might happen once or in stages, and it might affect the whole grid or just one reel.
Pick any two games to see how differently they grow; Cygnus 2 and Vikings make a good start.
Compare how two slots use Expanding Reels
Choose two games to see what triggers a larger layout, which positions change and how long the expansion lasts.
At a glance
| Cygnus 2 | Floridaman | |
|---|---|---|
| What triggers expansion | Another winning Avalanche occurs. | Mystery Splits activates randomly in the base game or bonus. |
| How the grid changes | Each winning Avalanche adds a row at the top, growing the grid from four to a maximum of eight rows. | One reel gains two or three positions, filled with copies of the same randomly selected symbol. |
| How long it lasts | In ordinary paid play the height resets for the next spin. The Free Drops height rule is not confirmed in our research. | The extra positions last for that spin, then the affected reel resets before the next spin. |
Explore the grid-expansion rules
Expanding reels do not always mean adding a whole new reel. Some games unlock more rows, others reveal extra symbol positions or extend the grid sideways. Expansion can build during consecutive wins, arrive at the start of a bonus, or enlarge a bonus feature’s own layout. The comparisons show what actually changes in each game.
Cygnus 2
Expansion featureWin-driven row expansionBase game and features
- What triggers expansion
- Another winning Avalanche occurs.
- How the grid changes
- Each winning Avalanche adds a row at the top, growing the grid from four to a maximum of eight rows.
- How long it lasts
- In ordinary paid play the height resets for the next spin. The Free Drops height rule is not confirmed in our research.
Sources: In-Game Rules and Paytable Screenshots
Floridaman
Expansion featureMystery Splits reel expansionBase game and features
- What triggers expansion
- Mystery Splits activates randomly in the base game or bonus.
- How the grid changes
- One reel gains two or three positions, filled with copies of the same randomly selected symbol.
- How long it lasts
- The extra positions last for that spin, then the affected reel resets before the next spin.
Sources: In-Game Rules and Interface Screenshots
What can actually expand?
The six games below show how different a larger playing area can look, and how long each one lasts.
| Game | What changes | Example behaviour | How long it lasts |
|---|---|---|---|
 Cowboy Coins |
One edge reel | A filled special-symbol edge reel gains one extra position. | Rest of the Free Respin feature; once per reel |
 Folsom Prison |
Locked reel positions | Previously inactive cells open inside a larger lockable structure. | Varies by game mode; the bonus rounds start with more cells open |
 Floridaman |
Individual reel height | Mystery Splits can add 2 or 3 symbol positions to one reel. | That spin only |
 Vikings |
Whole play area | Raid Spins change the structure from 5×3 to 7×5. | All of Raid Spins, then back to 5×3 |
 Fire in the Hole 2 |
Rows | Each qualifying collapse activates another row, up to six active rows. | That collapse sequence; a new paid spin starts at three rows |
 Concrete Cowboys |
Rows and columns | A collected Level Up symbol expands the grid by one row and one column. | Carries into the Bonus game, which starts at the current size |
Sometimes only one reel grows. Alongside Floridaman’s Mystery Splits, Mental 2‘s xWays feature reveals three symbols of the same paying type and makes the affected reel taller, without the rest of the grid changing.
What makes a reel or grid expand?
Almost anything the designer chooses. In Cowboy Coins an edge reel has to fill with special symbols. Floridaman‘s Mystery Splits are random. Vikings changes shape when Raid Spins begin. Concrete Cowboys grows when a Level Up symbol is collected. In Fire in the Hole 2, every collapse adds a row, and Cygnus 2 adds one with each winning Avalanche.
So “reels that grow after a win” is too narrow a definition. Wins can do it, but so can a feature starting, a random event or a collected symbol.
How long does the larger grid last?
Anything from one spin to a whole feature. Floridaman‘s Mystery Splits are gone before the next spin. Cowboy Coins can extend each edge reel once, and it stays extended for the rest of the Free Respin feature. Vikings holds its 7×5 layout throughout Raid Spins, then returns to 5×3.
Fire in the Hole 2 and Cygnus 2 work on the shorter timescale of a single sequence. Fire in the Hole 2 can grow from three rows to six, but the next paid spin starts again with three. Cygnus 2’s extra rows reset for a new paid spin too, while its Free Drops bonus has its own rule.
Base game or bonus?
Floridaman’s Mystery Splits can happen in the base game or a bonus, while Cowboy Coins and Vikings only expand inside their features. So seeing a bigger grid during a bonus doesn’t tell you how it got there or how long it’ll stay.
Expanding Reels and Ways to Win
If a game pays through Ways to Win, opening new positions can change the number of possible winning combinations.
Folsom Prison starts with only the two middle rows of reels 1 to 4 open and reel 5 locked, which is where its 16 starting ways come from. As cells open, the reels grow towards a full 4-6-6-6-4 layout, and the bonus rounds start with more of it already open: 2-4-4-4-2 in Walk The Line Spins and 4-4-4-4-4 in The Chair Spins. Nolimit City doesn’t publish a maximum ways figure, so I haven’t given one. Folsom Prison is one of three Nolimit City games on this page, along with Fire in the Hole 2 and Mental 2, and growing the grid is a good example of the innovation in their games.
Cygnus 2 starts with four rows and 4,096 ways. Each winning Avalanche can add a row, up to eight, where the published ceiling is 262,144 ways.
Ways aren’t required, though. Concrete Cowboys pays through ELK’s CollectR mechanic, and its Level Up symbol still adds a row and a column. Expansion and the payout method are separate rules.
Expanding Reels vs Cascading Reels
Cascading Reels replace symbols and evaluate the result again. Expanding Reels change how much of the grid is playable. The two can happen together, but neither automatically causes the other.
In Fire in the Hole 2, the Collapsing Mine removes and replaces symbols, and each collapse also activates another row, whether it followed a win, an xBomb or Wild Mining. One system keeps the sequence moving; the other enlarges the grid.
What is Win-Driven Reel Expansion?
Win-Driven Reel Expansion is the narrower case where a qualifying win is what grows the grid. Cygnus 2, where every winning Avalanche adds a row, is the example on this page; the dedicated guide goes into it properly.
Expanding Reels vs Expanding Symbols and Giant Symbols
These terms sound close, but they’re not interchangeable. Expanding Symbols spread across positions that already exist. Giant Symbols occupy several existing positions as one oversized symbol.
With Expanding Reels, it’s the active playing area that changes. More cells become available, rather than one symbol simply covering a larger area.
Are Megaways slots the same as Expanding Reels?
Not quite. A Megaways game changes the height of its reels from spin to spin anyway. It’s easy to see why the two get mixed up, because a reel getting taller looks much the same on screen either way.
The difference is that Expanding Reels need a specific event that makes the grid bigger. A game can have both, but variable reel height on its own isn’t expansion.
Expanding Reels FAQ
Can just one reel expand?
Yes. In Mental 2 and Floridaman, a single reel can become taller without the whole grid expanding.
Do Expanding Reels always increase the number of Ways?
No. Some Ways games gain more combinations when the grid grows, but Ways are a separate payout system. Concrete Cowboys expands without using Ways at all.
Does a bigger grid mean more wins?
Not on its own. More positions can mean more ways, and Cygnus 2 goes from 4,096 to 262,144, but that doesn’t tell you the RTP, how often the game pays or whether the expansion works in your favour.
Sources reviewed
I checked these games against developer documents, in-game rules and paytable material. Some evidence is only available through in-game or authenticated sources; the public links identify the games.
AvatarUX
NetEnt
Nolimit City
Pragmatic Play
ELK Studios
Where this guide comes from
I use the games’ own rules to check when the playable layout grows and how long that change lasts. If the source doesn’t settle a detail, I don’t fill the gap by guessing. Read the full research methodology