Random features slots can start a bonus effect on any spin without a scatter or trigger symbol: extra wilds appear, a multiplier lands, or a modifier reshapes the reels. They feel spontaneous, but each one has a fixed chance per spin set in the game's maths, so a feature you haven't seen for a while is no more likely on the next spin.
A random feature can fire on any spin; no symbol combination is needed.
Each has a fixed chance per spin: at 1 in 100, about 37% of 100-spin sessions see none at all.
UK online games must be random and cannot adapt to hit a target return.
On UK machines, 'random' and 'compensated' are different models, and the label should tell you which.
What it is
A feature that can trigger on any spin without a trigger symbol
Common forms
Random wilds, multipliers, mystery symbols, reel modifiers, random jackpots
How it's decided
By the RNG when the spin starts
UK online rule
Adaptive or compensated games not permitted (RTS 7)
Machine label
'This game is random' or a compensated notice (draft standards)
What random features slots are
Most slot bonuses need a trigger you can see: three or more scatter symbols, a full meter or a special symbol on a set reel. A random feature skips that step. The game simply decides, on any spin, to add something: a handful of extra wilds, a multiplier on the win, a symbol that transforms into another, an extra reel or a jackpot round. Designers use them to make the base game feel lively between bonuses.
You will see them called random features, base game modifiers, mystery features or surprise features. Many of the specific mechanics have their own pages, such as random wilds, mystery symbols and reel modifiers. This page covers what they have in common: how they are decided, how often they come, and what they mean for your budget. All of these sit in our slot features hub.
One value decides whether a random feature fires on this spin, using a probability set in the game's maths model.
If it fires, further values decide which feature, how strong it is (how many wilds, which multiplier) and where it lands.
The reels and the feature are then shown as an animation, often with a build-up, but the result is already fixed.
Wins are paid. Many random features are designed to make a win more likely when they fire, but not every one ends in a win.
Two points follow. First, the build-up animation is presentation: a shaking screen or a teaser spin does not mean the result is still in play. Second, the feature's chance does not depend on what happened before, so there is no such thing as a feature being overdue on an online slot.
Types of random feature in online slots
Common random features and what they do
Feature
What happens
Usual effect on wins
Random wilds
Extra wild symbols are added to the reels
Raises the chance of a line or way win on that spin
Random multiplier
A multiplier is applied to the spin's win
Larger payout if the spin pays
Mystery symbol reveal
Blank or mystery symbols all turn into the same symbol
Can create large matching groups
Reel modifier
Reels expand, split or gain extra rows before the result
The maths: how often will you see a random feature?
Developers rarely publish the exact chance of a random feature, so the figures below are illustrative. If a feature has a chance of 1 in N per spin, the probability of seeing it at least once in a session is 1 − (1 − 1/N) raised to the number of spins.
Chance of seeing a random feature at least once
Chance per spin
In 50 spins
In 100 spins
In 250 spins
In 500 spins
1 in 50
63.6%
86.7%
99.4%
Over 99.9%
1 in 100
39.5%
63.4%
91.9%
99.3%
1 in 250
18.2%
33.0%
63.3%
86.5%
Read the table the other way round, too. A feature that fires once in 100 spins on average will be missing from about 37% of 100-spin sessions, and a 1 in 250 feature from two-thirds of them. At 20p a spin, 250 spins stake £50; at 96% RTP the long-run average cost is £2, but whether the random feature turns up in that session is pure chance. Our page on bonus trigger odds applies the same formula to scatter bonuses.
Slots that use random features
The examples below come only from our verified slot facts. Where the facts don't list a detail, the game's help screen is the place to check.
Random features on fruit machines: random or compensated?
On UK fruit machines, features often appear to start at random: a sudden offer of nudges, a hold, or a jump onto the feature trail. Whether they truly are random depends on the machine's model. Many fruit machines are compensated: the controller tracks takings and payouts and steers features so that the machine returns close to its target percentage over time. On such a machine a 'random' feature is more likely when the machine has paid out less than its target, and less likely after a run of payouts.
That is why the label matters. The Gambling Commission's proposed gaming machine technical standards include notices that say 'THIS GAME IS RANDOM' or, for compensated games, that the game is compensated and may be influenced by previous play. Our guide to reading a machine label shows where to find that information, and the gaming machine categories (opens in a new tab) page sets the stake and prize limits each feature has to fit within.
Random and compensated models compared
Random model
Compensated model
Where
All UK online slots; some machines
Many UK fruit machines
Does past play matter?
No
Yes, the controller tracks takings and payouts
Feature timing
Fixed chance on every spin
Steered towards a target percentage
Can a player read it?
Nothing to read
No: the internal position is hidden
Pub machine limits
Category C: £1 stake, £100 prize
Category C: £1 stake, £100 prize
In neither case can a player gain an edge. Using an offered nudge or hold well avoids missing a win the machine has offered, but no technique beats its built-in payout percentage. Categories B and C are 18+ only.
How random features change volatility and cost
Random features usually lower the gap between memorable moments without changing the RTP. A game that pays part of its return through random wilds will tend to have more frequent mid-sized wins than one that saves everything for a scatter bonus, which can mean lower volatility. Random multipliers and random jackpot triggers work the other way, concentrating value into rare spins. The help screen often gives a volatility rating; our page on hit frequency explains what that does and doesn't tell you.
Random feature myths and facts
Advantages
Fact: each spin's chance of a random feature is the same on an online slot.
Fact: build-up animations start after the result is already fixed.
Fact: random features are part of the published RTP.
Fact: UK online games may not adapt to how much you have lost.
Drawbacks
Myth: random features fire more often when you are losing.
Myth: you can trigger them by changing stake or pausing between spins.
Myth: a feature that hasn't appeared for 300 spins is about to come.
Myth: a teaser animation means the feature nearly fired.
Random features must work inside the UK's online slot rules, in force since 31 October 2021: no autoplay, a minimum of 2.5 seconds per game cycle, no turbo or slam-stop, and no celebrating a return that is equal to or less than the stake. That last rule means a random feature that fires but leaves you with less than you staked cannot be presented as a win. On stakes, the online cap per spin has been £5 for adults of 25 and over since 9 April 2025, with a lower £2 cap for 18 to 24-year-olds from 21 May 2025.
Games must also show their rules and the RTP or likelihood of winning before you play, and payouts and probabilities can't be changed while a game is available. Our UK slot game design rules page dates each rule.
Where to play random feature slots online in the UK
Random feature slots are among the most common games in UK lobbies, but individual titles come and go, so use each casino's search before you register. Free demo play, available after age verification, is a good way to see how often a game's random features fire before you stake anything.
Our partner offers are for new customers aged 18 and over; terms apply. Coral: deposit and bet £10 or more on slots for 100 free spins on selected games, 10p each, with 48 hours to accept and 7 days to use them and no wagering on winnings (1 October 2026 to 1 February 2027; certain payment methods excluded). Ladbrokes: deposit and spend £10 on slots for 50 free spins a day for the first ten days, up to 500, 10p each on selected games, to be claimed by 23:59 each day and used within 7 days, no wagering (certain payment methods excluded). PlayOJO: 80 free spins on Big Bass Bonanza at 10p each for a first deposit of £10 or more, no wagering, new UK customers outside Northern Ireland. Because Coral and Ladbrokes share an operator (LC International Limited), check the terms if you already have one account. More on Coral is on its casino page.
Random features can make sessions feel unpredictable, so decide your budget first. Deposit limits, time-outs and reality checks are in your account settings at every UK-licensed casino.
Coral and Ladbrokes are both run by LC International Limited (Entain). If you already hold an account with one Entain brand, you may not be able to open a new account with another; check the terms before signing up.
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Read the Coral reviewLicence: LC International Limited, UKGC account 54743. Offer checked 5 October 2026.
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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.
Frequently asked questions
What are random features in slots?
Random features are effects that can start on any spin without a scatter or trigger symbol, such as extra wilds, a multiplier, a mystery symbol reveal, a reel modifier or a jackpot round. The game's random number generator decides on each spin whether one fires and how strong it is, using probabilities set in its maths model. They are part of the published RTP. Our pages on random wilds and mystery symbols describe two of the most common types.
How often do random features trigger?
It depends on the game, and developers rarely publish exact rates. As an illustration, a feature with a 1 in 100 chance per spin appears at least once in about 63% of 100-spin sessions and is missing from about 37%. A 1 in 250 feature appears in only a third of 100-spin sessions. The chance per spin never rises because you have waited. See our pages on bonus trigger odds and how many spins until a bonus.
Are random features more likely when I'm losing?
Not on UK online slots. Games licensed by the Gambling Commission must produce random results and may not adjust outcomes to reach a target return, so a losing run has no effect on the next spin. Some UK fruit machines are compensated, which means their features do respond to what the machine has taken and paid, but you can't see that position and other players affect it. Read are slot machines rigged and the compensated machines explainer.
Can I trigger a random feature on purpose?
No. The decision is made by the random number generator when the spin starts, and nothing you do, whether pausing, changing stake or playing at a certain time, changes the probability. Raising your stake only makes any win, and any loss, larger. On fruit machines you may be offered holds or nudges, which are choices within what the machine has decided to offer. Our pages on can you trick a slot machine and slot machine tips cover what genuinely helps.
What does 'this game is random' mean on a machine?
It tells you the machine's results don't depend on previous play, so features and wins come by chance on each game. Some UK machines are instead compensated, meaning they steer results towards a target percentage over time, and the Gambling Commission's draft machine standards require those to say so. Either way the machine must show its theoretical target return if it is Category B or C. Our guides to reading a machine label and how much a fruit machine pays out explain more.
Do random features change a slot's RTP?
No. A random feature is part of the game's maths model, so its average value is already included in the RTP. What it changes is how the return is spread across spins. Random wilds that fire often can make a game feel steadier, while rare random multipliers or jackpots make it more volatile. The RTP stays the same either way. See our pages on RTP and slot machine maths models.
Why did a random feature fire and not pay anything?
Because firing and paying are separate. Most random features are designed to make a win more likely on that spin, but extra wilds can land where they don't complete a line and a multiplier only matters if there is a win to multiply. Under UK rules the game must not celebrate a return equal to or below your stake, so an empty feature should be shown plainly. Read what a dead spin is and why a slot win did not celebrate.
Are random feature slots good for small budgets?
They can be, if the features fire often and are modest, because the base game returns more of its value along the way. Games that save their value for rare random jackpots or big multipliers are the opposite: long quiet runs with occasional large results. Check the volatility rating in the help screen and choose a stake that gives you enough spins. Our pages on the best slot for a small budget and slots for small budgets help.
Can I see random features in a free demo?
Yes, after age verification. Since May 2019, free-to-play demo games at UK-licensed casinos are only available once your age has been verified, and demo versions must reflect how the real game behaves. A demo is a fair way to see what a game's random features look like and roughly how often they appear, though a short demo session can mislead just as a real one can. See our demo slots guide and are free slot games the same as real ones.
Gambling can be addictive. Free, confidential help is available 24 hours a day from the National Gambling Helpline on 0808 8020 133. Visit GamCare.org.uk and GamCare, or block yourself from all UK-licensed gambling sites with GAMSTOP.
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