Reel modifiers in slots

What reel modifiers slots are

A reel modifier is any feature that alters the reels for a spin after the game has decided to apply it. The game might drop extra wilds onto the grid, turn a reel wild, convert low symbols into a premium one, attach a multiplier, add rows or strip out the lowest-paying symbols. Some modifiers fire at random in the base game; others are handed out at the start of free spins or chosen from a pick screen.

The word covers a broad family. Many of the features listed on our features hub can work as modifiers: random wilds, wild reels, symbol upgrades, multipliers and random features in general. What makes something a modifier is that it changes the reels themselves rather than giving a separate bonus game.

Common reel modifiers and what they do

Studios combine several on one spin. A game might add a multiplier and random wilds together, and free spins often keep a modifier active for the whole round, for instance with symbols removed until the bonus ends.

Megaways: the best-known random reel modifier

The most successful reel modifier of all is the one behind Megaways. The mechanic is a random reel modifier: on every spin, each reel shows a different number of symbols, so the number of ways to win changes. On six reels of two to seven symbols, that is anywhere from 64 to 117,649 ways.

Its creator, Big Time Gaming, introduced it in Dragon Born and later licensed it to other studios. Blueprint Gaming’s licence was announced on 1 May 2018, as CasinoBeats reported at the time (opens in a new tab), and Gambling Insider covered BTG licensing its patented mechanic and Megaways trademark (opens in a new tab) to other suppliers. Our Megaways history page tells the full story.

How reel modifiers fit inside the RTP

A slot’s RTP is the sum of everything it pays back, split across the base game, modifiers and features. Designers allocate each part a share. The breakdown below is invented to show the idea; no real game’s split is quoted.

The arithmetic for any one modifier is simple. If a modifier fires on 1 spin in 50 and its spins pay an average of 7× the stake, it returns 7 ÷ 50 = 0.14 of the stake per spin, or 14p in every £1, matching the row above. To make modifiers more frequent or stronger, the designer must take value from somewhere else, usually ordinary wins. That is why games with lively modifiers often have long runs of small or no wins between them.

The modifier frequencies in this section are illustrative. Developers don’t usually publish them, and we don’t quote trigger rates that aren’t on a developer’s own page or in our checked data.

How a reel modifier is triggered and applied

1. You place a stake and spin. The RNG decides the full outcome, including whether a modifier applies.
2. If a modifier is part of the result, the game plays its animation: a character throws wilds, a reel lights up, symbols transform.
3. The modified grid is shown and wins are counted on it.
4. In free spins, a modifier chosen at the start may stay active for every spin of the round.
5. Your balance updates with the net result, and the next paid spin starts fresh.

Because the outcome is already fixed, a modifier animation that ends with a small win isn’t a near-win of something bigger. It is simply how the game chose to show that result. The random number generator explainer covers why.

Reel modifiers slots in our checked data

• Rage of the Seas (NetEnt, 2020): 96.04% RTP, high volatility, 1,024 ways rising to 5,488 with Boost symbols. Free spins run on 5,488 ways with random modifiers.
• Blood Suckers Megaways (Red Tiger, 2023): 97.66% RTP at the top version, 324 to 117,649 ways, 20,521× max win. Free spins are preceded by a coffin pick game that adds modifiers.
• Big Bass Halloween 2 (Reel Kingdom, 2024): 96.71% RTP at the top version, 10 fixed paylines, 5,000× max win. Free spins come with a wild progress bar, multipliers and optional modifiers.
• Rotten (Hacksaw Gaming, 2022): 96.27% RTP, 6 × 5 grid, 35 paylines, 10,000× max win, with SwitchSpins respins alongside a jar-pick route into free spins.

For the Blood Suckers Megaways figures, slotcatalog’s Blood Suckers Megaways listing (opens in a new tab) carries the same grid details. Lower RTP versions exist for several of these games, so check the help screen at your casino.

Reel modifiers, volatility and cost per spin

Modifiers that fire often and add modest value make a game feel busier without raising volatility much. Rare, powerful modifiers, especially big multipliers, raise it sharply. The help screen’s volatility rating is the best guide.

Cost per spin depends only on your stake and the RTP. At Rage of the Seas’ 96.04%, 100 spins at 50p (£50 staked) cost about £1.98 on average; at £2, the limit for players aged 18 to 24, 100 spins (£200 staked) average £7.92. At Blood Suckers Megaways’ top setting of 97.66%, the same £200 would average £4.68, if the casino runs that version. Sessions vary widely around these averages.

Do fruit machines have reel modifiers?

Pub machines have their own versions. Features that add number reels, feature-board steps or a repeat chance change what a spin can pay, and many machines run a cash pot or similar extra. On a Category C machine everything stays within a £1 stake and £100 top prize. These features are part of the machine’s target payout percentage, which must be displayed but has no legal minimum.

Myths about reel modifiers

Under the Gambling Commission’s standard on generating random outcomes (RTS 7) (opens in a new tab), adaptive behaviour that changes probabilities during play is not allowed. There is no “due” modifier, as our slot machine myths guide explains.

UK rules for reel modifiers slots

Online slots supplied to Great Britain have had no autoplay, a minimum 2.5-second spin, no turbo or slam-stop and no celebration of returns at or below the stake since 31 October 2021. Stake limits are £5 per spin for those aged 25 and over and £2 for 18 to 24-year-olds. Some overseas versions let players pay extra for boosted spins or direct bonus entry; that isn’t offered at UK-licensed casinos. Our bonus buy in the UK and slot game design rules pages explain both.

Where to play reel modifiers slots

Search our partner casinos’ lobbies for the game by name; availability changes, and we don’t say a casino carries a title unless its own facts confirm it.

Offers for new customers aged 18+, with full terms: Coral gives 100 free spins when you bet £10 on slots (10p each, selected games, 48 hours to accept, valid 7 days, no wagering on winnings). Ladbrokes gives 50 free spins a day for 10 days, up to 500, after you deposit and play £10 on slots, with no wagering. PlayOJO’s welcome is 80 no-wagering free spins on Big Bass Bonanza for a first deposit of £10 or more, with any winnings paid as cash. Certain payment methods don’t qualify, and Coral and Ladbrokes share an operator.

Keep play affordable: set a deposit limit and a session time before you start, and call the free National Gambling Helpline on 0808 8020 133 if you need support.

18+. Gambling should be entertainment that costs money, not a way to make it. Decide a budget before you play: plan a slot budget. Free, confidential help: National Gambling Helpline 0808 8020 133.