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The Complete Online Slots Guide

Online Slots Guide

Online and mobile slots have seen an incredible rise in popularity over the past few years. Today, they’re some of the most played online casino games around, and there’s good reason for this; online slots allow you to stake a relatively small amount of money per spin, and – occasionally – allow you to win many thousands of times your bet from a single spin.

So if you’re wondering what it’s all about, look no further. This complete guide to online slots will tell you absolutely everything you need to know.

In this article, I’m going to be taking a close look at all aspects of slot games, from their origins to the best places to play mobile slots today. I’ll also show you how they work, how to play them – and what sort of wins are possible.

By the time you finish reading this online slots guide, you’ll be ready to start playing slots for real money like a pro.

History of Slot Machines

Vegas slot machine Of course, online slots are still relatively new, when compared to the history of gambling. Historians have managed to trace slot machines as far back as 1891.

Back then, a US manufacturer called Sittman and Pitt released what’s widely considered to have been the first “commercial” slot machine. The game utilized a number of physical drums (5 in total) and used real playing cards to display the results of the spin. In order to play, you needed to insert a physical coin in the slot machine and pull a lever.

In 1895, an entrepreneur called Charles Augustus Fey released a machine called the Liberty Bell. This proved a major turning point in the slot machine world, and it was the first game that awarded payouts for matching symbols on what are now known as paylines. The Liberty Bell could be found in bars and clubs throughout the USA.

It wasn’t until 1964, however, that slot machines started to attract mainstream appeal. Bally – a developer who is still producing slot machines today – released a slot game called Money Honey. With a 500-coin jackpot on offer on each spin, players now had a real chance of winning a decent bit of cash – and it was a notable machine as it was the first to award payouts without requiring an attendant to hand-pay it.

As technology improved so did the slots. In 1976 the first video slot was released, by a company called Fortune Coin. The game was offered at the Hilton Hotel in Las Vegas, and used a 19-inch Sony TV to display the result of the spin.

Since then, hundreds of slot developers have appeared, and today you’ll find a plethora of slot machines in every hotel in Vegas, and every other brick and mortar casino in the world.

But you don’t need to go to a brick and mortar casino to play slots. There are also new video slot games built using Flash and HTML5 technology – ensuring they can all be played online, and from your mobile devices.

Types Of Slots

Generally speaking there are four main types of slots; classic slots, 3D slots, video slots and progressive slots. In the next part of our online slot guide, I’m going to talk a bit about what each of these is, and how they work.

Classic Slots

small classic slot 777 Classic slots are pretty similar to the ones you’d have come across in land-based casinos many years ago.

They are (generally) built around a 3-row, 3-reel format and there’s usually just one (sometimes three) paylines.

Classic slots tend to carry the stereotypical slot machine symbols – think 777, three bells, cherries, bar symbols and so on. They don’t tend to offer any bonus rounds or free spins features, but this typically means that the line-win payouts are greater than their counterparts.

Video Slots

Video slots are the bread and butter of today’s slot machine industry. They’re found at virtually every online casino (and in every land-based casino) on the planet, and hundreds of millions of spins are put through them each and every day. Video slots work in a slightly different way to classic slots; the games don’t use physical reels.

Instead, a computer-generated image displays the result of the spin on screen. Video slots also tend to have exciting bonus/feature rounds built into them. This is most commonly seen in the form of free spins rounds, but also also includes “pick me bonus” rounds. I’ll talk about these a bit later on.

3D Slots

3D slots get an honorable mention here – despite functioning in an identical manner to the video slots I just covered. The difference with 3D slots is that the design of them is – as you can probably imagine – 3-dimensional. This doesn’t change the gameplay in any way, shape or form, but it does present quite a unique experience to you when you’re playing.

Many players report that they enjoy 3D slots as it adds an additional element of “being involved” – some of the better-designed 3D slots really do have graphics that stand out.

Progressive Jackpot Slots

progressive jackpot slot Progressive slots are another highly popular type of slot machine – found again, at all the best online and mobile casinos on the planet. These games have progressive jackpots attached, allowing you to win millions – or more – from a single spin.

A progressive jackpot slot is one that shares a pooled jackpot. This means that each time you play the slot, a tiny proportion of your stake is deducted and added to this pool.

Any player who is playing the slot contributes equally – and when a lucky winner scoops the jackpot, they’ll win the entire amount!

To ensure that progressive jackpot slots start with an attractive jackpot amount, most slot game developers will have a fixed “seed”. For example, Microgaming – one of the world’s biggest software providers – tends to “seed” all of their progressive jackpot slots with $1 million, so the starting jackpot is incredibly healthy!

Slot Features & Bonuses

Online slots have evolved significantly since their creation; today, you’ll see many features and bonuses built into most games, which are triggered when certain bonus symbols land on the reels. Below, I’m going to talk about some of the most common of these.

Free Spins

I’d say around 90% of all video slots on the market today contain a free spins bonus in one form or another. Free spins are usually triggered by landing 3, 4, or 5 of the scatter symbols anywhere in view and doing so will award you a certain number of free games. These games are played at your original stake, and some slots will also add various enhancements during the free spins too, giving you even more chances of hitting big wins.

“Pick Me” Bonus

Found in – I’d say – around 40% of online slots, “pick me bonus” rounds are also typically triggered by landing 3, 4, or 5 of the scatter symbols anywhere in view. Upon triggering it, you’ll be prompted to pick from a variety of symbols on screen. These picks can award everything from cash prizes and bet multipliers to free spins – and even progressive jackpots.

In-Play Bonuses

First made famous by UK-based developer Blueprint Gaming, in-play bonuses are like little side games that trigger randomly during the base-game. They can award a number of different features and perks including direct entry to the main free spins bonus, wild symbols and more.

Desktop and Mobile Slots: What’s The Difference?

One of the things I’ve seen change exponentially over the past few years is the way in which players are actually choosing to play slots. For example, 5 years ago it was all but unheard of for players to play online slots from their mobile devices.

This has changed dramatically, however, and now many game developers develop mobile-specific slot machines, designed to cater to players gaming from their smartphones and tablets.

On the face of it, online slots look – and play – pretty similarly to their desktop counterparts. The main difference is found with the actual layout and some of the behind the scenes work.

Best Mobile Slots Apps & Casinos

Desktop computers and laptops generally have bigger processors than mobile devices. This means that they can handle a higher level of graphics – without affecting speed. If these slots were to be played from mobile devices “as is”, however, the mobile device would heat up. The game would begin to lag – and the playing experience would suffer.

Mobile slots are designed to be much more accessible to mobile users. They’ll typically have some of the more unnecessary graphics cut out – and the background graphics will also be “toned down” a bit.

Game developers may also change the configuration of the buttons to make them more accessible. Mathematically, however, desktop and online slots are identical.

RTP & Volatility: An Introduction

If you’ve ever tried playing slots before – or have read anything about them – you may well have seen the phrases RTP and volatility thrown about before. I know – first hand – that these terms can be quite confusing at first, and that’s why I want to dedicate the next section of this guide to looking at what they are and how they affect your gameplay.

So, let’s start off with a look at RTP – what is it?

The RTP stands for Return To Player – and it’s a percentage format designed to give you an idea of how much money you can expect to receive back from a slot. Let’s imagine that a slot has an RTP of 97%.

This means that on average, for every $100 wagered through that slot, the online casino would expect to make $3 – the player could expect to receive back $97.

Of course, the RTP is determined over the course of millions of spins, and in the short term it’s not overly relevant. However, it does give you an indication of how volatile a slot machine is, which is what I’m going to cover next.

Generally speaking, online slots can either be low, mid or high in volatility. A low volatile slot machine will pay frequent wins – but these wins will be small. A highly volatile slot, on the other hand will deliver fewer wins – but much bigger ones when they do land.

Rules Of Online Slots

One of the reasons why mobile slots are so popular with players today is their simplicity. Unlike casino table games, video slots also don’t really have rules so much. However, in this section I’m going to do my best to give you an overview of how to play online slots – and what to expect.

  1. So, first of all you need to choose which slot you’d like to play. There are – literally – thousands of games available today, produced by hundreds of different game developers. Later in this post I’m going to give you an idea of some of the top slots to play (in terms of their RTP and win-potential) so stay tuned.
  2. Once you’ve loaded up the slot you’d like to play, you’ll then need to select your bet size. Some online slots have just one fixed bet amount – others allow you to change the number of coins and the coin value. It all results in the same thing – and it’s just an additional way of letting you customise how much you’re staking on each spin.
  3. Once you’ve selected your stake, you’re ready to play – just hit the “Spin” or “Play” button, and the reels will begin to spin. That’s it! Any winnings will be automatically credited to your account, and you can then begin the next spin.

Now, there’s two slot functions I’m going to make you aware of – you’ll see these in virtually all mobile video slots today.

The first, is what’s known as autoplay. This allows you to set the slot to play up to 100 spins automatically without you needing to click the spin button each time.

Some online slots also feature a “quick spin” option, which allows you to spin the reels faster than normal; a useful feature for those wanting to get as much gameplay as possible.

Top Online Slot Games

As I mentioned earlier, at most of the best online casinos you’ll find yourself faced with – quite literally – thousands of slots online to choose from. So which ones should you play?

Below, I’m going to show you some of the most popular games. These games will include a mixture of high RTP slots, and those offering massive win-potential. You can click on the links to our reviews to learn more about each game, and find a good online casino to play it.


Starburst Starburst is arguably the most commercially successful slot machine ever released – and it’s again, a game to come from Sweden’s NetEnt studios. You’ll find Starburst at virtually every online casino on the planet – and that’s not an exaggeration.

Set in a futuristic space-themed world, Starburst doesn’t contain a free spins feature per-se, but offers some exciting base-game play. If, during the base-game, you land one of the Starburst symbols on the middle three reels you’ll trigger the re-spin feature.

This sees the Starburst symbol transforming the whole reel wild before locking in place for a re-spin. It’s possible to transform the middle three reels into wild reels – allowing for some mega win-potential!

Starburst Slot Review

Book of Dead

Book Of Dead Another of the world’s most successful slot releases (and one of my personal favourites) Book of Dead is an Egyptian-inspired slot from Swedish developer Play’n Go.

It follows the life of Rich Wilde – a bold adventurer who does his best to uncover vast treasures in the midst of pyramids and tombs. There’s not a huge amount going on in the base-game – it’s the free spins bonus where you’ll find the real action. This is triggered by landing 3, 4, or 5 of the scatter symbols anywhere in view.

Do so and one symbol will transform into an expanding scatter; this means you simply need to land two or more of the symbol anywhere in view, and it will expand to fill the entire reel, paying all paylines accordingly!

Book of Dead Slot Review


Bonanza slot logo Bonanza (a video slot from Australian game developer Big Time Gaming) may not offer the highest RTP of the games on this list – but it certainly offers some of the biggest win-potential.

This slot game uses the now-famed Megaways mechanic, which sees the number of ways-to-win varying on each spin. Massive wins can be formed during the base-game, but it’s the free spins feature you’ll want to keep an eye on. (This bonus round is by far my favourite.) During it, there’s an unlimited multiplier which increases on every successful cascade win.

There’s no limit to how high this multiplier can get – and it’s also possible to re-trigger an unlimited number of free spins too, so there really is unlimited win-potential.

Bonanza Slot Review

Mega Moolah

blank Mega Moolah is the first progressive jackpot slot to make the list, and this slot game is produced by industry leader Microgaming.

It’s known for being the most successful progressive jackpot slot in history, and it regularly offers jackpot amounts worth in the tens of millions of dollars.

There’s also a free spins bonus, during which all wins are multiplied by 6X – plenty of potential for those wanting the chance to win life-changing sums of money!

Mega Moolah Slot Review

Immortal Romance

Immortal Romance Another of Microgaming’s “classics”, Immortal Romance is arguably one of the best-known slots ever made. It’s based loosely around Twilight – and there are four main characters; Amber, Troy, Micahel and Sarah.

There’s lots of exciting features to look forward to, the first being the “Wild Desire” bonus. This is randomly triggered during the main base-game, and turns between one and all five reels wilds.

There’s also the “Chamber of Spins” bonus that lets you pick one of four different free spins features.

Immortal Romance Slot Review

Dead or Alive

Dead or Alive 2 Another online slot game from Swedish developer NetEnt, Dead or Alive is set in the Wild West of the US.

It’s known for offering some of the biggest win-potential of any non-jackpot slot, and the main bonus round is triggered by landing 3, 4, or 5 of the scatter symbols anywhere in view. Do so and you’ll be awarded with 12 free spins. During the free spins, all wilds are “sticky”. This means that they lock in place.

If you manage to land 5 of the wild symbols on an active payline you’ll hit the acclaimed “wild line”, which pays massive amounts of money. You can also win an additional 5 free spins by landing one wild symbol on each of the five reels.

Dead or Alive 2 Slot Review

Sakura Fortune

Sakura Fortune logo Sakura Fortune is the first slot game to appear from Quickspin on this list – another well-known game developer from Sweden. Sakura Fortune is based around a stunning Japanese emperor, and you’ll see her taking the form of stacked wilds; these can appear on reels 2, 3 and 4. During the base-game, these wilds can nudge up to fit the entire reel they land on – but it’s the bonus round you’ll want to keep a close eye on.

Triggered by landing 3, 4, or 5 of the scatter symbols anywhere in view, during the bonus the wild Sakura symbols become sticky – locking in place for the remainder of the bonus. You will also receive one additional free spin for each wild symbol that you manage to lock in place.

Sakura Fortune Slot Review

1429 Uncharted Seas

1429 uncharted seas 1429 Uncharted Seas is a video slot from a game developer known as Thunderkick.

The game is famed for its incredibly high RTP – most sites have it running at a staggering 98.6%. That means that, on average, you’ll only lose $1.40 for every $100 you wager through it. You’re unlikely to find a higher RTP when playing slots online!

Surprisingly, the slot can also dish out some pretty healthy-sized wins. A thrilling free spins bonus sees special wild symbols added to the reels, making it possible to land a full screen of wilds if the stars align!

1429 Uncharted Seas Slot Review

Blood Suckers

Blood Suckers logo Blood Suckers (the original, not the remake) is another slot which is famed for its high RTP. This online slot game from Swedish developer NetEnt carries an RTP of 98%.

It’s incredibly high – especially in today’s online gambling world – and it’s not uncommon for online casinos to restrict this game from being played using bonus funds due to the chance of players easily converting the bonus. There’s a couple of bonuses to be found in Blood Suckers including a “pick me bonus” and a free spins feature.

Blood Suckers Slot Review

Pay Tables

Virtually every video slot on the planet contains something called a pay table. This is found from within the game itself, so every online casino that has the game will display the same information. It is usually found under a “?” icon or a button labelled by Pay Table. The pay table is an incredibly important facet to the game as it gives you an idea of “what’s what”.

Book of Dead paytable
Paytable from Book of Dead slot

The pay table serves two main purposes; the first, is to give you an idea of how much each winning combination pays. This shows you how much a 3-of-a-kind, 4-of-a-kind and 5-of-a-kind combo pays – and many pay tables are now dynamic, which means they automatically adjust depending on which stake size is currently selected.

The second purpose of the pay table is to show you how the game’s various bonuses and features work.

For example, if the slot contains a free spins feature, you’ll be able to view information about how to trigger it. You’ll see what bonus symbols you need, whether there’s any options you can choose – and what to expect during the bonus itself.

Most pay tables will also display information about the slot’s RTP, and, where relevant, will also show you the slot’s version number if it’s recently been updated.

Choosing The Best Online Slots

You may be wondering about how to choose the best online slot – what I will say, is that a lot of the time it simply comes down to personal preference. Sure, you can choose a slot that offers a high RTP or one that offers big win-potential – but ultimately you’ll want to try and choose a machine that you actually enjoy.

Today, you can play online video slots covering virtually every genre. You’ll find titles set in the ancient realms of China, while others are set in futuristic metropolises – all encompassing incredible, HD graphics.

Many online casinos now allow you to play video slots in “demo play” too. This lets you test out the slots without risking any of your own money – of course, you won’t win real money, but it’s a great way of getting a feel for how a slot works and what you can expect to experience when playing it for real money.

I’d always recommend you take a bit of time to check out slot games you actually enjoy – and don’t feel forced into playing a certain game just because other players rave about it or tell you it’s the “best” game out there.

Slots Tournaments

Slots tournaments are becoming an increasingly popular aspect found at many online casinos. They allow you to play all of your favourite slots – without (necessary) risking as much of your own money.

As a general rule of thumb, slots tournaments are designed to be played around a player-vs-player approach. This means you pay a “buy in” and then get to play on the slot for free – with the player who’s done the best at the end scooping a prize.

While many of you may not be familiar with the idea of playing slots tournaments, they’ve actually been played for decades. They were first made popular in Las Vegas casinos, many years ago.

They were a great way of enticing players into playing slots, while allowing them to enjoy playing for slightly less than they would were they playing every spin for the full price.

In the online world, slot tournaments were especially popular at their own downloadable casinos. They lost popularity in the early 2010’s, although in the last few years they’ve made quite a comeback.

If you’re looking to play video slots for a relatively small stake – and want to enjoy the excitement of playing alongside other players (while also being able to win some pretty sizable amounts of money) then they’re a great way to ‘get your money’s worth.’ I personally really enjoy slot tournaments as they give me the chance to play different slots I probably wouldn’t normally play.

Last Updated on November 2, 2020