The Ultimate Online Casino Guide

Updated: June 1, 2023 11:42

Online slots is an online gambling application that produces a set of random numbers visualized as symbols across several reels (3 or 5 reel slots). The way that a software manufacturer connects similar symbols to count toward your winnings is called a payline.

All slots are hosted and run from the manufacturers' servers, online casinos are being only providers of access to them, i.e. intermediaries in fact. So, whenever you play online slots for free or in an online casino for real money you actually play it on the slots manufacturer’s premises, online casino only takes and pays back your money. Online casinos cannot change the gameplay or distribution of winnings in any specific slot.

Best Online Casinos to play Slots in Ireland
King Billy Review
King Billy Casino
100% up to €500 + 100 Free Spins

Allows Bitcoin. Live Chat option available. Award-winning casino. Offers Bitcoin games.

Playamo Review
Playamo Casino
100% up to EUR100 +100 free spins

Efficient customer support, well-thought usability, countless promotions for new and regular players, varied payment options, fast withdrawals 

N1 Review
N1 Casino
100% up to €1,000 + 150 free spins (1st dep)

Award-winning casino, popular in many countries, reputable licence, multiple bonus offers, VIP program.

Rizk Review
Rizk Casino
100% up to €200 + 50 Free Spins

Withdrawal up to 24 hours on average, top-tier software suppliers, mobile-friendly design, full time live chat

21 Review
21 Casino
121% bonus up to €300 & 21ND FS

Reputable operator, rich library of games, a great signup offer

PlayLuck Review
PlayLuck Casino
UP TO €800 + 130 EXTRA SPINS

Secure payments, Malta and UKGC License protection. Good welcome bonus offer

Twin Review
Twin Casino
100% up to €200 + 200 Spins

Wager-free rewards, strong licence coverage and website protection, welcome incentives for Irish players, high Cashout Limits.

Wildz Review
Wildz Casino
100% up to 500€ + 200 FS

Chat availability 24/7, mobile compatibility, good selection of payment options

Buran Review
Buran Casino
up to €500 + 200 FS

Proven fair games, support of cryptocurrencies, huge gaming portfolio

Woo Review
Woo Casino
up to €/$100 + 150 Free spins

Home to a huge number of games by multiple software providers, various banking options, loyalty program and ongoing promotions

CasinoEuro Review
CasinoEuro Casino
100% Bonus up to €1000 + 100 Wager-Free Spins

Larger daily payouts than in average Irish online casinos, good reputation since 2002, trustworthy casino secured by MGA license, VIP programme, wager-free spins for new players

Bizzo Review
Bizzo Casino
up to €400 and 150 free spins

Massive collection of games, welcome bonus package, VIP club, and variety of payment methods, including crypto

Lucky Days Review
Lucky Days Casino
100% up to €500

Decent bonus enticements, quality software, a good collection of slots games

Slots Magic Review
Slots Magic Casino
100% to EUR100 + 50 FS

A huge selection of games, Best software providers, reputable casino operation with a trustworthy licence coverage.

National Review
National Casino
up to €100 + 100 Free Spins

Games from top-tier software providers, bonuses, promotions and tournaments, VIP program, live chat support available 24/7

7Bit Review
7Bit Casino
100% up to €300 + 100 FS

Enormous collection of casino games, including BTC provably fair slots, instant games etc. Customer support 24/7. Wild bonuses

Casino Kingdom Review
Casino Kingdom Casino
40 Free Spins for €1 and 1 NDFS

Extensive collection of Microgaming games, Minimum deposit Casino, Around-the-clock support through live chat, email, and toll-free phone call options, Verified fair and trustworthy by eCOGRA.

SpinAway Review
SpinAway Casino
up to € 100 + 100 FS (1st deposit)

1,000+ casino games from leading software companies, fast payouts, mobile compatibility

Jackpot City Review
Jackpot City Casino
up to 1,600EUR

Reputable operator, high overall RTP%, minimum deposits available, impeccable customer service

Spin Review
Spin Casino
Match Bonus up to 400€

Fast Withdrawals, live chat is accessible 24 hours a day, seven days a week, SSL encryption, mobile apps


Slots manufacturers are audited by such organizations as eCogra, etc to produce a fixed return on a player's money over a large number of spins (usually, millions of spins). This theoretical value of an online slot to a player is called Return to Player (RTP). For example, The Highest Payout online slots by NetEnt are:

  • Jackpot 6000
  • Dead or Alive / Dead or Alive 2
  • Reel steal
  • Wild rockets
  • Jungle Spirit Call of the Wild
  • Wild turkey
  • Secrets of Christmas
  • Secrets of the Stones

As you can see the payout is negative (less than 100%), so a player may think he/she would lose on average about 5 cents from every dollar each time he/she spins the slots. Yet, the idea of RTP is different: you will be losing your 5 cents in the long haul, yet, till that time you may win (go green) and lose (go red) a number of times, and you don’t exactly when it happens. How to predict when you will win on a slot machine?

To do that, it’s important to understand how online slots actually work. Let’s take the example of NetEnt slots: they use the Pyramid principle, which means that all players form a prize pool from the money they have lost. In theory, if you are the only player who plays in a wholly new online casino in a specific slot, the prize pool is empty and is only filled up with your money. So, you will be losing all the time till you are fed up with the prize pool and it will start to pay you back your own money. In this case, you will get back 90-95% of the amount of your deposit. This is what RTP really is.

Now, NetEnt manufacturer takes about 2-5% of the prize pool to themselves and distributes the rest of the money pool (RTP) to all players that have come to play this game. There are different levels of distribution of the prize pool: by a casino, by the online slot game, and by the wager value.

The prize pool is distributed separately by every single online casino, so could only potentially get the prize pool formed by players who lost their money in the casino that you play. The same concerns specific online slots: you may only win what others have lost on a specific online slot that you play.

Wager value or the size of your bet is how actively you contribute to the forming of the prize pool. There are 4 levels of online slots players by the contribution to the prize pool:

  1. Low bets players (usually making €0.1 to €5 bets)
  2. Bonus hunters (usually making €5 to €10 bets, i.e. betting towards the max wager limits when playing with bonus money)
  3. Medium bets players (€10 to €50 bets)
  4. High rollers (€50 to max allowed bet)

At any level (except for the High Rollers) from 1% to 10% of the accumulated prize pool go to the higher stakes’ prize pool for the big winning. Likewise, Low bets players would have a portion of the prize pool they formed passed onto the next level, i.e. Bonus hunters. The same concerns those making €5 to €10 bets. Since the game is underway between players and an online casino would only take its small part, players essentially compete with each other for the prize pool: the more players at each level, the less chance to win big.

Obviously, the medium value of bets (€10 to €50 bets) is the most profitable wagering limit for hitting a big win. At these limits, there are much fewer players than above, but here are collecting money from previous limits (the bets from €0.25 to €10), and are much fewer participants in the "drawing" as put it.

Software providers must disclose the odds of winning on specific slots and these data form dependencies. They disclose the maximum win, probabilities of hitting any winnings (and how they are distributed towards normal play and bonus play mode) as well as probabilities of hitting two wins in a row. This value forms the following dependencies:

  • The Higher the max win, the longer the cycle of winning, i.e. when a slot machine starts to pay back big.
  • The higher the Volatility (also called Variance or Dispersion) of Winnings, the less predicted the size and frequency of winnings at the end of the cycle.

In potentially ‘big win’ slots, you can wait for many rounds till you get any winnings (have lots of empty spins). Therefore, fewer people would play it and the cycle of winning does depend on the prize pool too.

Quick reference guides:

  • Top-paying online slots
  • Best Slots for wagering the bonus money
  • Best High Volatility slots
  • Best Free Spins slots
  • Best Multiplier Slots
  • Best slots 2019
  • Best New slots
  • Best Classic slots
  • Best Video Slots

Reviews and Lists of the Best online slots from software manufacturers:

  • Best Netent online slots
  • Best Microgaming online slots
  • Best Aristocrat online slots
  • Best Playtech online slots

Slot Games Definitions

Paylines:  Paylines run across the slot screens as well across all reels in a horizontal, diagonal or zigzag pattern. A payline gets activated as you bet on it. When a composition of symbols forming the winning symbols emerges on an activated payline, you win that game and the payouts coming with it.

Reels, which are an essential feature of any slot machine, are wheels that have printed symbols. On pressing the ‘spin’ button, the reels start moving and come to a stop finally. It is the positioning of symbols on wheels that determines a winning combination. The symbols that a slot game may contain conform to the game itself. For instance, the Beach Life Progressive Slot by Playtech a beach theme comes with beach-themed symbols.

Multiplier: Generally, the Wild symbol is the multiplier. True to its name, it multiplies. So, in case a winning combination contains the multiplier, your payout gets multiplied by two, three, or even more times. In other words, it becomes the fastest payout.

Wild Symbol: You’ll find these online as well as classic slots. They can replace any symbol but not the scatter symbol for making a winning combination.

Scatter Symbols:  called so because they may be scattered everywhere on the reels and can make you win. Usually, a player is required to have two or more scatters on two or more paylines for winning that round. Before you start placing bets on slot games, you need to decide the coin size you would like to play and the number of paylines you would like to be activated.

Selection of coin size is done by pressing the plus (+) button for increasing the coin denomination or the minus (-) button if you want to play with a lower denomination. The number of pay lines you want to activate is done by clicking on ’select lines.’ And, this is how you can calculate the total amount of your bet. Suppose you choose a coin value of €0.25, with 3 paylines along with 5 coins. So, the total amount of your bet would be 0.25X3X5=€ 3.75 Online slots are provided with a payout plan, which tells you how much you’ll get paid on winning various combinations. So, you don’t have to use your calculator as the needed information is instantly provided by all slot games. Here’s an introduction to various types of slot machines.

Types of Online Slots

Classic Slots

When you like playing a traditional online casino game, especially old-fashioned slot machines, you would find Classic Slot Machines fulfilling your requirements. The first online edition of these games was developed by Microgaming in 1994.

Fruit Fiesta (or recent re-incarnation Happy Fruits) and Cash Splash are among the oldest online slot games. Initially, they were coming in three reel editions but now you get five reel editions too. These are quite easy to play, compared with other complex slots as generally they generally lack unusual symbols like Bonus Symbols, Scatter Symbols, and Wild Symbols. Other leading companies like Playtech and Cryptologic have developed Classic Slots.

Rags to Riches from Cryptologic is among popular Classic Slots that are connected to a progressive jackpot too. Tomb of the Pharaoh, a Classic Slot from Playtech with the looks of a land-based mechanical slot machine has all the real sounds that are heard in a land-based casino. However, it doesn’t offer progressive jackpots.

Here are Classic slots/slots details:

  • Number of reels: 3
  • Number of paylines: Varies from three to five
  • Wager: Can be one, two, or three coins
  • Winning combination: A paying symbol must appear in reels of an activated payline to trigger wins. Usually, there is just one symbol that allows winning though it may appear on a single reel only.
  • Free spins: Generally, classic slots don’t offer free spins or bonus games with some exceptions that you may find in Aristocrat slots.
  • Software: Aristocrat, Playtech, and Microgaming provide extraordinary classic slots.

Play Video Slot Games Online

The basic difference between classic slots and online video slots is that the latter comprises five reels against three in the case of classic slots. However, there are many other differences too. Video slots have more visual appeal. Current video slots generally display wins via computer graphics to heighten the visual effect. Well-known slots based on popular TV shows or movies display animation by way of short video clips.

Generally, themes of such slots include a sport, natural beauty, or ancient civilization. The backgrounds of the wheels plus symbols accentuate the theme. These are identified by their bonus features, the most popular of which is the free spin feature. As this feature gets activated, you are allowed to play many spins for which you won’t have to place any bets. The other admired feature is the bonus game on a second screen. The most usual form of this fixture demands you to select items to award you with random bonus payouts. Here are some of the most admired video slots: South Park, Iron Man-3, Wipeout, Where’s the Gold, Fruit Stack, Magic Portals and Dragon Island, etc.

Jackpot Slot Games

In case of Jackpot Slots, also known as Progressive Slots, the value of the jackpot keeps increasing by small amounts at the end of each game which is not won by any player. In the past, jackpot slots were individual games but the present trend is to connect different slots to the same jackpot. This results to having one big progressive jackpot that grows faster as a number of players keep contributing to it simultaneously and it can be hit by any of the contributive slots.

Have you ever had a lot of free time in your hands that you don’t know what to do with it anymore? That’s only normal; what’s also usual, is that you wish to find something productive that you can do with your time, and the good news is, there are plenty of things that you can do! We all have different tastes and enjoy various activities – that’s what makes us human – but if you wish to make money while having fun, we’ve got the solution for you. It’s time that you join an online casino and start taking advantage of all that it has in store for you. It will definitely be one of the best experiences you could live in your life, and you shouldn’t miss out on it!

A meter displays the number of jacks at all times. As a player gets the jackpot, the jackpot amount is adjusted to a predefined minimum level. It is a large number of jackpots that attracts many players. This amount is often prominently displayed on electronic displays. Another kind of jackpot slot is known as the multi-level progressive jackpot. In this case, various jackpots with varying amounts are connected to the same network of slots.

Top 10 Best Free Online Slot Games List

Haunted Hospital
Haunted Hospital
Wild Scarabs
Wild Scarabs
Exotic Cats
Exotic Cats
Jack Hammer 2
Jack Hammer 2
Immortal Romance
Immortal Romance
Jurassic Park
Jurassic Park
Jack and the Beanstalk
Jack and the Beanstalk
Reel Talent
Reel Talent

Helena Kay
Created by Helena Kay