Online Slots

Top Slot Games & Casinos

Rainbow Spins Casino
Welcome Bonus
🎁 Win Up to 500 Free Spin + 100% Bonus
Our Score
Welcome bonus for new players only. Maximum bonus is 100% up to £100. Min. deposit is £20. No max cash out. Wagering is 35x bonus. Maximum bet with an active bonus is £5. Eligibility is restricted for suspected abuse. Cashback is cash with no restrictions. Skrill & Neteller deposits excluded. Cashback applies to deposits where no bonus is included. 18+.T&C apply
Online Slots
Top Slot Games & Casinos
Final thoughts

If you’re a slots fan is the right place for you. We’re passionate slots players and are eager to share our decades of experience playing slots at brick and mortar, as well as online casinos. We have listed the best rated slot games as well as casinos for your Geo location to play your favourite slot games hassle free.

All you need to know about slots online

If you’re a slots fan is the right place for you. We’re passionate slots players and are eager to share our decades of experience playing slots at brick and mortar, as well as online casinos. On this page, you will find a highly detailed explanation of how online slots work, which slots have the best payout, and what you can expect to find at online casinos. Keep on reading and feel free to share your opinions.

How do online slots work?

Slots are the driving force of the online gambling industry mostly because of two reasons. The first one is that slots are incredibly easy to play. You don’t need to learn any rules or use any betting strategy since they’re completely games of chance. All you need to do is set the bet size and hit the spin button. The rest is up to lady luck whether you win or lose.

The second reason is that slots can pay considerably higher amounts than any other game at the casino. Some progressive jackpot slots can change your life awarding multimillion jackpots all while playing on the minimum bet. This has been known to happen and is reason enough for many players to try their luck, hoping for mega-million payouts. But how exactly do slots online work?

Best Online Slots Game

FAQ about online slots

1. Can I play slots from a mobile device?

Yes, you can play slots from any mobile device. The slots are designed with the HTML5 protocol meaning that they will run seamlessly on all devices, regardless if it’s an iPhone, iPad, laptop, desktop, or an Android smartphone.

2. Can I play jackpot slots with a bonus?

This depends on the casino itself and the bonus promo. Most casinos don’t allow you to play jackpots with an active bonus, especially if it’s a no deposit bonus. Make sure to check the bonus terms of the promo before you start playing the games.

3. Which provider has the best slots?

The leaders in the online gambling industry are Microgaming and Net Entertainment. But there are also a lot of other providers which have great slots in their offer.

4. Will I be paid in full if I win the jackpot?

Yes, usually progressive jackpot wins are paid in full and in a single transaction. This is because progressive jackpot wins are paid out by the game supplier and not by the casino itself. So if you win the jackpot on Mega Moolah you will be paid by Microgaming themselves.

5. Are slots fair?

Yes, all online slots are fair and random in terms of payouts. They are games of chance, meaning that it’s only up to lady luck whether you win or lose. Furthermore, many reputable operators also employ independent testing agencies. These agencies test the slots monthly and confirm that the payouts are within the promoted parameters.

Rules and Tips

What you see on the screen

The first thing you notice about slots is simply what you see on the screen. Slots follow a general design and are different in the number of reels, rows, pay lines, and symbols. Let’s take a look at what each one is.


Reels are vertical fields where symbols land. Most slots in the industry today follow a 5 reels’ design. But this can differ from one game to another. The older classic slots all followed a 3 reels’ design, while modern slots can have 6 or even 7 reels. Despite these variations, it seems that players respond best to the standard 5 reels’ slot design.


Rows are horizontal fields that go across the reels. The older classic slots followed a single row design, while video slots adopted the 3 rows design. Just like with the number of reels there are many slots today which have 4, 5, 6, or even more rows. These slots have a much bigger number of pay lines or ways to win and are known to be able to produce big payouts.


Paylines are simply positions on the reels and rows where symbols need to land for a win to be formed. With pay lines, the symbols must land on the imagined line for you to get a winning combination. The number of pay lines varies from one slot to another. It can be from a single pay line up to 100 or more on some modern slots.

Ways to Win

The Ways to Win design eliminates the need for pay lines across the reels. Instead, you need to land matching symbols on adjacent reels for a win to be formed. The Ways to Win design is adopted by modern slots and their number can be in the hundreds of thousands.

Regular Symbols

Slots symbols are responsible for forming the payouts on the reels. The math is simple. Land 3 or more matching symbols on a winning pay line and you are awarded a payout according to the paytable. The symbols in the game usually follow the slots theme and add to the visual appeal of the slot.

Special Symbols

The special symbols in slots come in the form of a Scatter, Bonus, and Wild symbol. The Scatter and Bonus symbols have pretty much the same function. Once 3 or more of them land on the reels the corresponding bonus feature is triggered.

The Wild symbol is often referred to as a Joker symbol. Its function is to replace all of the regular symbols in the game. In most cases, the Wild also has the highest payout from the rest of the game symbols. This is why landing a 5 of kind Wild win is the highest payout you can get in a big number of slots.


The audio is an important part of online slots. Many slots have interesting background sounds as the reels’ spin and a recognizable coins sound when a win is formed. Some designers take the audio one step further adding short songs to the bonus features. In this context, Immortal Romance by Microgaming was selected to be the slot with the best sound theme in the entire industry.

Help and Payouts

The help and payouts button is there to help you better understand the game. When you click on the help button you will see what the bonus feature is, as well as the way it’s triggered. The payout button on the other hand shows you the payouts the symbols can produce, as well as the maximum payout per spin or in the bonus feature

Random Number Generator

Now that you know what’s going on in front of you it’s time to move on to the processes behind the screen, starting with the Random Number Generator (RNG). Slots are games of chance and the piece of software responsible for that is the RNG. It makes sure that every spin on the reels is completely random and in no correlation with the previous one. This is why you simply can’t predict what will happen next as you play the game.

The slot can shell out two scatters every 3-4 spins without triggering the bonus round for 500 spins. On the other hand, you can get the feature on the very first spin. This is exactly what makes slots so interesting and borderline addictive to play. You never know how a slot is going to behave and whether you will win big or go broke. It all comes down to the RNG and lady luck.

Return to Player (RTP)

Every slot machine, land-based or online, comes with a predetermined Return to Player (RTP) value. This value is encoded by the manufacturer of the slots and can’t be tampered with in any way. For example, a slot can have an RTP value of 96%. This means that over a given number of spins the slot will pay back 96% of all bets in the form of winnings. It will only keep 4%, which is the house edge. So in the long run the expected profit from that slot alone will be 4%.

But this doesn’t mean that if you put in $100 in a slot machine you can expect to win only 96%. That’s not the way slots work. This is when the RNG and the slot Variance come into action, creating a game of chance.


The variance on slots is the frequency of payouts it can produce. By seeing what the slot variance is you can see what to expect from the game in terms of payouts. In general, slots can be divided into 3 categories based on their variance.

High Variance

If you ask an experienced slots player which are the best online slots and the worst ones to play in terms of variance the answer is High Variance slots. How is this possible? Well, high variance slots are known as money eating machines which can easily make thousands of dollars from your bankroll disappear without a bonus round on the horizon. So how can they be the best slots to play at the same time? Well simply because they can also award a bonus round early on which can pay thousands of dollars. Simply put high variance slots are highly volatile machines that can make or break you at the casinos in one session.

Medium Variance

Medium variance slots are on the border among low variance and high variance slots. They can produce hefty payouts, but at the same time, they can also keep your balance steady while you’re wagering a bonus. Preferred by many players, medium variance slots are considered to be the safe choice when playing at online casinos.

Low Variance

Low variance slots are considered to be the babies among slots and not many players take them seriously. These are slots that produce frequent payouts, but most of the time they are small in size. These slots are perfect when you need to wager a massive bonus amount without losing too much of your balance. They are also great for playing on higher bets if you want to slowly and gradually increase your balance. But bear in mind that it will take a lot of patience and control to get ahead while playing low variance slots at the casinos.

Types of online slots

You have surely noticed that not all slots are the same. Some have attractive bonus features and state of the art visual details, while others are very simple and even dull to play. Here are the main slots types you can come across at online casinos.

Classic Slots

Classic slots are older games, also known as Vegas slots, which once dominated the casino floors. Online casinos decided to add these games to their slots offer as well, catering to the needs of nostalgic players. Classic slots usually don’t have any bonus features attached, but can pay big. This is because you’re usually playing with a single pay line and a strong paytable.

Video Slots

Video slots are modern games that have a lot to offer. They come with a modern design, state of the art animations, and attractive bonus rounds. Video slots have interesting gameplay so you can easily spend hours spinning the reels. Most of them come with great bonus features that can easily produce massive payouts.


Jackpot slots can come in the form of both classic and video slots. These are simply slots which have a jackpot prize attached. Some jackpot slots have a fixed jackpot prize, while others come with a progressive jackpot attached. In the case of progressive jackpots, the top prize is pooled over a series of slots or casinos, reaching incredible heights. The biggest recorded online jackpot win came on Mega Moolah by Microgaming, measuring 13 million pounds and was won on the minimum 0.25 bet per spin. This is why progressive jackpots are so popular among players, hoping that the next spin will be the lucky one which changes their lives forever. When you ask a player for a list of the top 10 slots to play in most cases a jackpot slot is always one of them.

Bonus feature

The bonus feature is the most attractive part of the slot game and this is where the biggest payouts can happen. A lot of players decide to play slots based on the bonus feature alone. Most slots come with a free spins bonus installed, but they can also have additional features, like a cash pick and win bonus. Based on the bonus feature and the symbol payouts you can easily see the payout potential the slots have and whether they’re worth playing or not. Let’s take a look at the most common bonus features you can come across when playing slots.

Free Spins Bonus

The free spins bonus is the most common feature you can come across at most slots. The concept is very simple. On most slots, you need to land at least 3 Scatters to trigger the feature. You are then awarded a number of free spins. Usually, most free spins bonus rounds come with extra features attached. It can be a win multiplier, sticky wilds, expanding wilds, wild multipliers, and so on. These features add to the payout potential of the bonus round and are the main reason why some slots can create massive payouts.

Cash Bonus

The cash bonus in most slots is considered to be the weaker feature. The reason for this is simply because the payouts which can land in the cash bonus are considerably lower than the ones which can come from the free spins bonus. But there are some slots where the cash bonus can award massive payouts. These slots are few and far between but are well worth playing.

Extra Features

The extra features which can come in the bonus round are what make slots so interesting. In most cases, the extra features are attached to the free spins feature or to the Wild symbol itself. In some slots, you can come across a combination of several extra features that make up for a powerful and interesting bonus round. Let’s take a look at the most popular extra features which you can find at most slots.

Reel Nudge

The Reel Nudge is an interesting feature that can be found at some slots. This feature can come in two cases. On some slots, it’s added as a means to increase the chance of triggering the feature. For example, if you land 2 Scatters on the reels and the third one misses by one position, the reel can nudge up or down and bring back the third Scatter on the screen.

In the second case, the Reel Nudge design is used on slots where you can choose which reel to nudge but it comes with a predetermined cost. These slots are interesting as sometimes you can hit some very nice payouts.

Reel Re-Spin

The Reel Hold feature can be found on a limited number of slots today and was first introduced by Microgaming on their video slot Hot Ink. The concept here is that you can choose to re-spin one reel on the screen for an unlimited number of times. But each spin comes with a cost to your balance so you need to take into consideration the payout you can land vs the overall cost of the re-spins.

Win Multiplier

The Win Multiplier is pretty standard on most slots with a free spins bonus. Once the feature is triggered all payouts will come with an attached win multiplier. On most slots the win multiplier is x3, but there are slots where it’s value can be much higher.

Cascading Reels

The Cascading Reels feature has become very popular nowadays. The slot which made this feature so popular was Gonzo’s Quest by NetEnt. The concept is very simple, yet can be very rewarding. Once a win is formed on the reels the symbols involved disappear. At the same time, new symbols land on top of the reels to fill in the missing spaces. This way you can get several winning spins in a row, all for the price of a single spin. Combined with other extra features, like a Win Multiplier, the Cascading Reels can award pretty hefty payouts.

Sticky Wild

For many players, the Sticky Wilds feature can be found only in the best online slots. Once a Wild lands on a reel it will remain in position for several spins, as long as it contributes to a winning combination or for the duration of the feature. If the Wild can land on all of the reels you also have a chance to win a Wild Line, which in most cases is the highest possible payout in the game.

Expanding Wild

Expanding Wilds are always a welcome sight across the screen. When a Wild lands on a reel it will expand vertically covering the entire reel. This feature gives you a chance for landing a full screen of Wilds and massive payouts.

Sticky Expanding Wild

The Sticky Expanding Wild is a great feature where the Wild expands to cover the reel and also remains in position for the duration of the feature. Not too many slots offer this feature but it’s a very attractive one, to say the least.

Stacked Wild

The Stacked Wild is a pretty standard feature. Instead of a single Wild, you can get 2, 3, or more Wilds to land stacked on the reel. With some luck this can happen on a few adjacent reels, leading the way to hefty payouts.

Transforming Wilds

Transforming Wilds is a feature that can be found in a number of UK slots. The idea here is that when a specific symbol lands on the reels it will be transformed into a Wild symbol.

Transferring Wilds

Not too many slots use the Transferring Wilds feature but it’s an interesting one to see. Usually found on more complex slots the idea here is that once a Wild lands on a certain position on the reels it is transferred to another position as well.

Random Wilds

Random Wilds is a feature that can be found in a big number of slots. It often acts as an additional Wild symbol, creating bigger payouts on the reels. In many cases, the Random Wild can come in sets of 3 or more symbols.

Extra Wilds

The Extra Wild feature can be considered to be the baby brother of the Random Wild feature. Its function is the same with the only difference being that the Extra Wilds usually land in a smaller number.

Walking Wilds

The Walking Wilds is also a very interesting feature, found in many new online slots. When a Wild lands on the reels it will begin to walk in any direction in every following spin. Usually, the Wild walks across the reels up until it leaves the screen completely.

Split Symbols

The Split Symbols feature can be found in a number of slots and can produce hefty payouts. The idea here is that a certain symbol can split into two or more symbols, awarding a bigger payout.

Double Symbols

The Double symbol is similar to the Split symbol, where a single symbol counts as 2 separate symbols. So if you get a 5 of a kind win with one Double Symbol the payout will count as a 6 of a kind win.

Regular payouts VS Feature Payouts

A lot of players make a mistake when deciding which slots to play based on the symbols’ payout. Some slots have very low top symbols payout, so you can easily dismiss them. Others on the other hand can have a high maximum payout, so you can rush to give them a try for real money. But before you do this you need to consider several factors.

The first thing to check out is whether the slot uses a pay line or a ways to win design. Bear in mind that slots with a ways to win design can create bigger payouts, especially if the symbols can come stacked on the reels. So even if the top paying symbol in the game awards a payout of 4 times the total bet, the payouts it can actually produce are much higher.

Another important detail to keep in mind is the bonus feature of the game. If the slot uses a pay line design with no stacked symbols and a free spins bonus with tripled payouts you know exactly how much you can win during the feature. For example, the top paying symbol in the game comes with 100 times the total bet payout. Now during the free spins, all payouts are tripled, so you stand to win a maximum of 300 times the total stake per spin.

But what you should consider is that this is the maximum payout the game can produce and payouts like this come once in a blue moon. So before you start playing a game make sure that the low and medium payout symbols have decent values and that the bonus feature has the potential for bigger payouts. This will make a difference in the long run, boosting your chances of winning.

Play slots with a bonus

Every experienced player will tell you that it’s better to play slots with a bonus than with a pure deposit. Even high roller players who deposit tens of thousands at once are always on the hunt for some attractive bonus. Why is this so?

Well, there are several reasons for playing with a bonus. The first one is that you can play on higher bets since you start playing with a bigger balance. In return you can easily hit a big payout and clearing the wager will be a piece of cake. After all what better way to win big than with some help of casino money.

The second reason is simply cutting down on losses. If you make a $200 deposit and lose it, you lost $200. But if you make a $100 deposit with $100 in bonus money and lose it, you only lost $100 of your real money. You can use the other $100 to deposit at another casino, claim another bonus and play again. Since slots are games of chance you never know where and when you’ll win big. This is why it’s better to try a few casinos rather than risk losing all of your money at a single operator.

Things to look out for when claiming a slots bonus

Pretty much all online casinos offer some sort of a bonus promo. It doesn’t matter if it’s a no deposit required bonus, as welcome bonus or some hefty free spins promo. You can easily claim it and play the slots. But when it comes to the terms associated with the promos they’re not all the same. Some promos are better than others, some come without wagering requirements and it’s always a good idea to do some research before you claim a bonus and start playing. Some of the most common terms to look out for at bonus promotions are:

  • Wagering requirements
  • Allowed slots for play with bonus funds
  • Maximum allowed bet per spin
  • Cashable or Non-Cashable bonus
  • Allowed Payment Methods to claim the promo
  • Timeframe allowed to play with the bonus

Play only at our recommended casinos

Before you start playing slots you need to choose where to play them. There are thousands of online casinos in the industry that specifically target UK and USA players. This makes the task of finding the top casinos, not an easy one to say the least. But have no fear as we at MOUGLE have a team of professional casino experts who do the hard work for you. They’ve put together a list of reputable online casinos that have the best offers of slots UK and best reviews. By playing at our recommended online casinos you know that you are protected at all times and your withdrawals are processed without any problems. All you need to do is choose a casino from our list and you can start playing online slots UK right away.