iGaming Updated Jun 2026 2 min read

What Is a Bonus Round in a Casino Game?

Triggered feature games inside slots and instant titles

In short:

A bonus round is a triggered feature inside a slot or instant game that pays out under a different rule set from the base game. Common formats include free spins, pick-and-click, multiplier ladders, and feature-buy mechanics. Bonus rounds typically account for a large share of total game RTP.

What is a bonus round

A bonus round is a separate gameplay phase inside a slot or instant title, triggered by a specific event in the base game: a scatter combination, a feature symbol stack, or a randomly seeded event. Once entered, the bonus round operates under its own pay mechanic, which can include free spins, locked wilds, expanding reels, multiplier accumulation, or a pick-and-click selection screen.

The certified mathematical model of the game accounts for both the base game and the bonus round. The bonus round often contributes the majority of total RTP, even though it is reached infrequently.

Common bonus-round formats

Free spins are the most common bonus-round format: a fixed number of spins at a defined stake with modified rules such as locked wilds or growing multipliers. Pick-and-click formats present the customer with a choice between hidden values. Wheel-of-fortune formats spin to a randomised reward. Cascading and re-spin formats extend base-game rounds under specific conditions.

Feature-buy is a newer mechanic that lets the customer pay a fixed multiple of stake to enter the bonus round directly. Feature-buy is restricted or banned in several regulated markets because it accelerates volatility and shortens decision cycles.

Why bonus rounds matter in B2B

For game providers, bonus-round design is a primary differentiator. Mechanics that resonate with customers can carry a title to long-term lobby performance. For operators, the bonus-round mechanic affects volatility, average session length, and the regulatory profile of the title in each jurisdiction. Feature-buy availability in particular is a per-market decision.

Frequently asked questions about What Is a Bonus Round in a Casino Game?

It varies by game. Many slots target a hit rate around 1 in 150 to 1 in 300 spins for the bonus round, though high-volatility titles can extend that to 1 in 500 or beyond. The certified mathematical model defines the trigger probability.

Yes. The total certified RTP includes both base-game and bonus-round contributions. In many modern slots the bonus round contributes 40% to 60% of total RTP, even though it is reached only occasionally.

Feature-buy lets the customer bypass the base game and pay a multiple of stake to enter the bonus round directly. Regulators in some markets, including the UK, have restricted the feature on the grounds that it accelerates stake velocity and weakens responsible-gambling protections.

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