The Basics
A free spins round (also called bonus round, bonus game, or feature) awards a set number of spins at no additional cost. During these spins, the maths model usually changes — wins multiply, wilds become sticky, or new mechanics activate that don't exist in the base game.
Free spins are the primary source of big wins in most modern slots. The base game is mostly a waiting room.
How Free Spins Are Triggered
| Method | Description | Examples | |---|---|---| | Scatter symbols | 3+ scatter symbols anywhere on the reels | Book of Dead, Gates of Olympus | | Special reel position | Scatters must land on specific reels | Many BTG Megaways titles | | Meter/progress | Fill a meter over multiple spins | Hacksaw Chaos Crew | | Bonus buy | Pay to skip to the feature | Most modern slots (UK excluded) |
Common Free Spins Mechanics
Sticky/Locked Wilds
Wild symbols that land during free spins stay in place for the rest of the feature. Each new wild multiplies potential wins on future spins.
Example: Dead or Alive 2 (NetEnt) — sticky wilds on a low-symbol reel count = enormous multipliers.
Cascading/Tumble with Multiplier
After each cascade (winning symbols removed, new ones fall), a multiplier counter increases by 1. It resets between spins but not between cascades. The multiplier can climb into the hundreds during a hot cascade chain.
Example: Gates of Olympus, Bonanza — these are the defining "big win" mechanics.
Expanding Symbols
One symbol is randomly chosen at the start of free spins. It expands to cover entire reels whenever it appears. If it lands on most reels, the whole board fills.
Example: Book of Dead, Legacy of Dead — the iconic "book" mechanic from Play'n GO.
Retriggers
Landing 3+ scatters during free spins awards additional spins without resetting the multiplier or wilds. Can significantly extend a good run.
xWays (NoLimit City)
A proprietary NoLimit City mechanic. xWays symbols expand to show 2–4 random symbols, effectively multiplying the number of winning combinations. Combined with xNudge wilds (that bring their multiplier with them), these create extreme high-variance swings.
Example: San Quentin, Tombstone, Fire in the Hole.
How Many Free Spins Is Enough?
The number of spins matters less than the mechanics. 10 spins with sticky wilds (Dead or Alive 2) can outperform 50 spins with no multipliers. Focus on:
- Does the multiplier persist across spins (Megaways cascade style) or reset?
- Are wilds sticky or do they disappear each spin?
- Can it retrigger? Even one retrigger on a Megaways game can change everything.
Volatility and Free Spins
High-volatility games typically front-load their expected value into the bonus round. The base game pays little; the bonus pays a lot — but triggers infrequently. When comparing two games:
- Low RTP base + high-paying bonus = high variance (Megaways, DoA2)
- Medium RTP base + medium bonus = medium variance (most Pragmatic Play titles)
- Good base + modest bonus = lower variance (Big Bass Bonanza, Fishin' Frenzy)
Practical Tips
- Never chase the feature by doubling stakes — that amplifies losses, not wins
- Demo the bonus before committing real money — many casinos let you buy into demo free spins
- Check the volatility on the slot page — that tells you how often you'll see the feature
- Session budget should assume 100+ base-game spins before the first meaningful bonus trigger on a high-volatility game