A complete breakdown of the bonus features that actually appear across modern online slots — wilds and their sub-types, multipliers, free spins and retriggers, re-spins, pick-and-click bonus rounds, cascading wins, ante bets — plus the specific UK regulatory position on bonus buy features that catches a lot of players out

Slot marketing throws around feature names — sticky wilds, walking wilds, mystery multipliers, ante bets — as if every player already knows exactly what each one does and how much it actually changes a game's math. Most don't meaningfully change the maths at all; they change how a game feels to play, and a smaller number genuinely shift the odds in your favour for a spin. This guide breaks down every major bonus feature you'll actually encounter on UK-licensed slots, what each one does mechanically, and — importantly — the specific UK regulatory position on bonus buy features that trips up a lot of players who've read about them elsewhere.

Wild Symbols and Their Sub-Types

A standard wild substitutes for other symbols to help complete a winning combination, the most basic and universal bonus feature in slots. But "wild" now covers a genuinely wide family of sub-types, each with a different practical effect:

Expanding wilds grow to cover an entire reel once landed, dramatically increasing the number of winning combinations that single symbol can complete — a single expanding wild on reel 3, for instance, can turn several near-miss combinations into paying ones simultaneously.

Sticky wilds stay locked in place across multiple spins or free spins rounds rather than disappearing after one spin, compounding in value the longer they persist — several of the walking-wild and sticky-wild mechanics covered in individual game guides on this site (NoLimit City's titles in particular) build entire bonus rounds around this persistence.

Walking wilds move one position (typically one reel to the left or right) after each spin, guaranteeing a specific wild appears in a different, still-useful position on the following spin rather than vanishing.

Stacked wilds appear multiple times on a single reel stacked vertically, increasing the probability that a wild lands somewhere on that reel on any given spin, without expanding or persisting the way expanding or sticky wilds do.

Multiplying wilds carry an attached multiplier — landing a 2x or 3x wild as part of a winning combination multiplies that specific win, distinct from a general win multiplier applied to the whole spin.

Multipliers

Multipliers increase the value of a win by a fixed or escalating factor — a 2x multiplier doubles the payout of the combination it applies to, and multiplier values on modern slots can escalate considerably higher during bonus rounds specifically. The mechanic appears in genuinely different forms: a flat multiplier applied to every win during a bonus round, an escalating multiplier that increases with each consecutive cascade or avalanche (the format popularised by Gonzo's Quest, covered in a dedicated guide on this site, where each cascade adds to a running multiplier), or a multiplier tied to a specific symbol or board position (as in Sugar Rush's multiplier-spot mechanic, also covered on this site, where specific positions on the board retain and compound their multiplier across repeated hits). The practical takeaway: "multiplier" alone doesn't tell you much — checking whether it's flat, escalating, or position-based changes how it actually plays out across a session.

Free Spins and Retriggers

Free spins award a set number of spins played without additional stake, usually triggered by landing a minimum number of scatter symbols (the mechanics of scatter triggers, including position-independent triggering and threshold requirements, are covered in more depth in this site's dedicated Scatter Symbols Explained guide). Free spins rounds frequently carry their own enhanced rules distinct from the base game — a higher win multiplier ceiling, additional wild symbols, or a different reel configuration entirely, as documented across several individual game guides on this site (Gonzo's Quest's Free Falls bonus extends its multiplier cap considerably beyond the base game, for instance).

Retriggering allows additional scatter symbols landing during an active free spins round to award further free spins on top of the original allocation, extending the round beyond its initial length — a detail worth checking on a specific game's rules screen, since not every title allows retriggering, and those that do vary in how many additional scatters are required.

Re-Spins

A re-spin feature locks a subset of the reels or specific symbols in place while re-spinning the remainder, giving additional chances to complete a winning combination without needing an entirely fresh spin. This is the foundation of the Hold & Win / Money Respin format — covered in detail in this site's Wolf Gold guide, where landing six or more "Money" symbols locks them in place and awards a fixed number of respins, with each new Money symbol landing during the respin sequence resetting the respin counter back to its starting value. This format has since spread well beyond its original slot machine roots into a huge range of modern online titles, usually built around a jackpot-style prize structure tied to how many symbols end up locked by the time respins run out.

Pick-and-Click Bonus Rounds

A pick-and-click (or "pick 'em") bonus round presents the player with a selection of hidden items — chests, cards, symbols — each concealing a prize, feature, or multiplier, revealed one at a time until the round ends (typically triggered by picking a specific "collect" or "end" item). This format is especially common on progressive jackpot titles — NetEnt's Hall of Gods, covered in this site's Progressive Jackpot Slots guide, uses a pick-and-click round themed around Thor's hammer to determine which of its three jackpot tiers a player wins. The format's appeal is largely presentational — it dresses up what's still a random outcome in a more interactive wrapper — though the specific prize pool being picked from does genuinely vary by which symbols remain in play as the round progresses.

Cascading, Tumbling, and Avalanche Wins

When a winning combination lands, the symbols involved are removed and replaced by new symbols falling into the vacated spaces, with the process repeating for as long as new winning combinations keep forming from a single initial spin. This mechanic — most closely associated with Gonzo's Quest, widely credited as the title that popularised the format industry-wide, covered in a dedicated guide on this site — has since become one of the most widely adopted slot mechanics in the industry, appearing under different branded names (Avalanche, Tumble, Cascade) across a huge range of modern titles, including frequently being paired with the Megaways mechanic (covered in this site's Megaways Slots Explained guide). The genuinely useful detail to check on any specific title: does the win multiplier reset after each spin, or does it persist and escalate within a single chain of cascades — this varies by game and meaningfully changes how a long winning streak within one spin actually pays out.

Collector and Meter-Based Features

A smaller number of titles build bonus features around a persistent meter that fills as specific symbols land, rather than triggering instantly off a fixed threshold. Play'n GO's Reactoonz, covered in a dedicated guide on this site, is the clearest example — its Quantum Leap system runs five separate meters (Implosion, Alteration, Demolition, Incision, and a fifth stage) that fill as matching alien symbols are destroyed during cascades, with each meter unlocking a different escalating in-game effect once filled, rather than a single fixed bonus round trigger. This is a genuinely different design philosophy from a standard scatter-triggered bonus — the feature builds gradually across a session's cascades rather than firing all at once.

Bonus Buy: The UK-Specific Catch

This is worth being direct about, because it trips up a lot of UK players who've read about bonus buy features from international gambling content. A bonus buy (or "feature buy-in") feature lets a player pay a fixed multiple of their stake — commonly somewhere between 50x and 150x — to skip straight into a slot's bonus round without needing to land the trigger naturally. This feature is not available on UK-licensed casino sites. The UK Gambling Commission didn't issue a single, named outright ban on the mechanic — instead, the position was formalised through the Commission's Remote Gambling and Software Technical Standards (specifically the requirement that products must not actively encourage customers to chase losses or increase their stake), enforced from around October 2021 onward. UK-licensed operators responded by releasing UK-specific builds of affected slots with the bonus buy purchase option stripped out entirely — the underlying game (a title like White Rabbit Megaways, for instance) remains fully playable at UK-licensed casinos, but the "buy bonus" button itself simply isn't there in the UK version, even though it may still appear in that same game's build on non-UK-facing sites.

The legal UK alternative is an ante bet (sometimes called a bet booster or feature bet) — this raises your total stake by a fixed percentage in exchange for an increased probability of the bonus round triggering naturally, rather than guaranteeing it outright. The distinction matters: an ante bet only shifts the odds, it doesn't guarantee the bonus, and the extra stake is paid on every single spin regardless of whether the feature actually lands — a meaningfully different proposition from an outright bonus buy, and worth understanding clearly before assuming the two work the same way.

How These Features Combine in Practice

Modern slots rarely rely on a single bonus feature in isolation — most combine two or more of the mechanics above into a single title. Wolf Gold pairs its Money Respin jackpot feature with a separate free spins round. Gonzo's Quest's cascading avalanche mechanic feeds directly into its Free Falls bonus, where the multiplier cap extends well beyond the base game. NoLimit City's titles, covered in this site's NoLimit City provider hub, are particularly known for stacking multiple proprietary mechanics (xWays, xNudge, xSplit) within a single spin rather than relying on any one feature alone. Understanding each individual mechanic in isolation — as covered above — makes it considerably easier to work out what a specific title's combination of features actually does, rather than treating an unfamiliar slot's feature list as an undifferentiated wall of marketing terms.

A Practical Checklist Before Playing

Check whether a multiplier is flat, escalating, or position-based — these behave very differently across a session even when a game's marketing describes them all simply as "multipliers."

Confirm whether retriggering is available during free spins — not every title allows it, and it meaningfully changes how long a bonus round can realistically run.

Understand that bonus buy is not available on UK-licensed sites — if a specific feature-buy price is advertised in non-UK content you've read elsewhere, expect it to be absent from the UK build of that same game, with an ante bet as the closest legal equivalent where one is offered.

Read a re-spin feature's specific reset rules — Hold & Win-style formats vary in exactly how many respins are awarded and whether the counter resets when a new qualifying symbol lands during the sequence.

Treat pick-and-click bonus rounds as presentational rather than strategic — the outcome is predetermined by the game's underlying RNG regardless of which items you choose to reveal.

Who This Guide Genuinely Suits

Good fit: players who've noticed slot marketing throwing around feature names inconsistently and want a genuine, mechanic-by-mechanic reference to check a specific game's features against — particularly useful before assuming a bonus-buy price advertised elsewhere applies to the UK build of the same title.

Less suited: players looking for strategy advice on which features to chase — bonus features change how a game plays and pays out, but none of them, including ante bets, provide a way to overcome a slot's underlying house edge.

Frequently Asked Questions

What's the difference between a sticky wild and a walking wild?

A sticky wild stays in the exact same position across multiple spins until the feature ends. A walking wild moves to a new position (typically one reel across) after each spin, so it doesn't stay in one place but also doesn't disappear immediately.

Can I still buy bonus features on UK-licensed slot sites?

No. UK-licensed operators removed the bonus buy purchase option from their UK builds of affected games following UK Gambling Commission technical standards enforced from around October 2021 — the underlying slot is still playable, but the buy-bonus button itself isn't present. An ante bet, where offered, is the legal UK alternative, though it only shifts the odds of triggering the bonus naturally rather than guaranteeing it.

Do cascading wins and free spins always come together?

No — cascading/avalanche mechanics and free spins bonus rounds are separate features that are frequently combined but don't have to be. Some titles use cascading wins purely within the base game with no dedicated free spins round, while others pair the two, as Gonzo's Quest does with its Free Falls bonus.

Does a bigger advertised multiplier always mean a better bonus feature?

Not necessarily — a high multiplier ceiling that's genuinely difficult to reach in practice may add less real value than a lower, more consistently achievable multiplier, and this varies enormously by the specific game's volatility and trigger frequency.

What's the difference between a re-spin feature and free spins?

Re-spins typically lock specific reels or symbols in place while re-spinning the rest, usually tied to a jackpot-style prize structure (as in Hold & Win formats). Free spins award a set number of full spins played at no additional stake, usually with enhanced rules like extra wilds or a higher multiplier cap.

Are ante bets available on every UK slot?

No — ante bets (or bet boosters) are offered on a per-game basis at the operator's and developer's discretion, not universally across every UK-licensed slot. Check a specific game's betting panel to see whether one is offered.

This guide is for informational purposes. Bonus feature availability, including ante bets and bonus buy restrictions, varies by specific game and by UK versus non-UK build — always check the individual game's rules screen for current, exact details before playing. 18+ only. UKGC-licensed operators only. Gambling problem? BeGambleAware.org | National Gambling Helpline 0808 8020 133. Information correct as of October 2026.