- What is Return to Player?
- What is Variance?
- Slot Games – How They Work
- Slot Games – Symbols
- Slot Games – Advanced Features
- Slot Games – Bonus Features & Bonus Rounds
- Slot Games – Progressive Jackpots
Let’s start with two very important concepts – Return to Player and Variance. You can start playing online slot games without understanding what they are, but it’s kind of like taking out a credit card without understanding what interest rates are.
What is Return to Player?
Return to Player is the percentage of total stakes that the slot pays back out to the players, averaged over millions of spins. Note that it is a percentage of stakes and not a percentage of deposits.
Let’s say you deposit £100 and start to play a slot with RTP 95% at £1 a spin. 100 spins later, your expected return would be £95 but what that means is that if thousands of players did the same thing, they would be left with £95 on average; it does not mean you will be left with £95 on this particular occasion and it could be much higher or much lower.
However much cash you have left after playing through the £100 you deposited, if you now continue to play you will be playing with money that has already been through the slot once – and that RTP of 95% applies every time you play it through. Your expected return on £100, if you keep on playing £1 spins, is down to under £50 with a little over 1000 spins (but the actual sum you have by that time may be nowhere near £50 and could be zero – see the explanation of variance below).
What is Variance?
Also known as volatility, variance is a measure of how drastically the slot is likely to deviate from the average return to player in one play session by one player – and how many spins are likely to be needed before the actual return to player settles down close to the expected return to player. If that sounds like gobbledegook, consider this:
A slot that has a very high paying and rather rare bonus round but which doesn’t pay out much during normal play has high variance. Do 100 spins on that slot and the chances are you’ll either come out ahead after triggering the bonus round at least once, or you’ll have lost most or all of your stake after not triggering it at all. Do 100,000 spins on the same slot and you’ll come out closer to the average.
With a low variance slot – which has smaller more regular payouts either during normal play or as a result of a more frequent and less extreme bonus round, the amount you will have left after a mere 100 spins will tend much closer to the theoretical return to player.
While it is fairly easy to find out the RTP of a slot (they have to be displayed somewhere on site, usually via a link from the Fair Play page or Terms and Conditions) it may not be as easy to find out the variance. Some slots such as Dead or Alive by NetEnt (and its sequel Dead or Alive II) are so notorious for their high variance that is not necessary to look very far in order to find out about it, but with a newly released slot it may not be obvious. These days, many slot games have a volatility rating which is displayed on the loading screen, but not all of them do. Taking a close look at the paytable can yield clues; if the 5 of a kind payouts are very high and the 2 or 3 of a kind payouts are low, that points to high volatility. Another tell-tale sign of high volatility is a bonus round with a feature such as an unlimited increasing multiplier.
A lot of players prefer the excitement of a high variance slot, but do remember that although it is possible to score a very big win on one of these the flipside is losing a lot of money depressingly quickly without ever getting to the exciting bit! It is also worth checking, if trying to play through a wagering requirement, that the high variance slot actually counts towards it as they very often don’t.
Got that? Now, let’s look at how slot games actually work and what all that terminology means.
Slot Games – How They Work
First, let’s consider the ancestor of all modern slot machines, online and offline – the classic mechanical fruit machine or one armed bandit. The one arm refers to the lever on the side that was pulled to make the reels spin, and bandit refers to them taking your money!
The slot games of today are a very far cry from that. As well as offering multiple paylines, bonus features, hugely entertaining sound and visual effects and the possibility of very big wins, modern online slot machines generally have a much better return to player than their mechanical ancestors; one armed bandits commonly had RTP of around 70% whereas the vast majority of online slots have RTP of over 90% and many have RTP of over 95%.
One armed bandits typically had three mechanically operated reels with symbols on them including fruits, and to win you had to spin up three of a kind in a line across the middle. In modern parlance that’s a 3 x 3 reels array with 1 payline – and there you have the basic mechanism of a slot machine.
Essentially, the slot machine pays out prizes for collecting sets of matching symbols. “Reels” determines how the symbols arrive in the play area and “paylines” determines whether a set of matching symbols wins a prize.
Not all modern slot machines have recognisable reels (more of this later) but when they do, it’s usually 5 or more reels instead of just 3. What’s more – and this goes for electronic slot games in a casino as well as online – the reels are virtual rather than mechanical with the stop position determined by a random number generator.
Virtual reels can include hundreds or even thousands of symbols (vastly more than could be accommodated within the confines of a physical machine) and this in turn means that the probability of getting a symbol that only appears once on the virtual reel, is much lower than the probability of getting a symbol that only appears once on the mechanical reel. This sounds bad for players on the face of it but actually it isn’t; what it does is allow much higher volatility.
Let’s say for the sake of argument that the virtual reel has 256 symbols and the physical reel 20; for a symbol that only appears once on each reel the probability of getting three of a kind of that symbol on the virtual reels is 1/256 cubed, which is 1/16,777,216. Whereas the probability of getting three of a kind on the physical reels is 1/20 cubed, which is 1/8000. The payout for three of a kind of that symbol on the mechanical reels is therefore going to be triggered more than 2000 times as often as it is on the virtual machine – and if the two machines have the same RTP the payout for three of a kind on the virtual machine can therefore be VERY much larger. Hello high volatility!
Another advantage of having virtual rather than mechanical reels is that it is possible to have a bonus round with either a completely different set of reels, or none at all (such as in a pick me type of bonus round). This is great for entertainment value!
The most common arrangement of reels to find on an online slot game is 5 x 3 – 5 reels with 3 positions visible on each reel. They might not look like reels though – instead, they could look like cascading gemstones or waves crashing on a beach.
Going beyond the classic 5 x 3, game providers have come up with all sorts of wild and wacky arrangements. For a start, reels don’t all have to be the same height; they can be part of a triangular array (Dazzle Me), a hexagonal array (Siberian Storm) or of variable height (any one of dozens of Megaways games). Nor does the number of reels have to be fixed; it’s common for the array to expand when a bonus feature is triggered but there’s also the Infinireels games where additional reels are added to the right of the array for as long as winning symbols keep coming up.
As online slot games get more and more inventive, many games go beyond an unusual array and break the concept of reels altogether. Jammin’ Jars 2 by Push Gaming looks more like a Candy Crush level than a slot machine, for example – and then there’s Finn and the Swirly Spin where the symbols spiral in towards the middle of the board.
Going back to those classic fruit machines, they had just one payline, running across the centre of the reels. It would be the symbols that appeared in those three positions that determined whether and how much you had won.
With online slots that have paylines, however, it is quite a bit more complicated; not only are there almost always multiple paylines (20-30 is very common and it can be up to 100) but apart from the occasional slot which pays both ways (Starburst is one of these) the combinations are counted from left to right only. What this means is that with 5 reels, to score for 2 of a kind they need to appear in position 1 and 2 of the payline to be counted. Only the highest scoring combination counts so with three symbols the same on a payline on reels 1, 2, and 3 you would only score for 3 of a kind, not for 2 of a kind as well. You would, however, score for each payline on which the combination appears and in the case of slots with lots of paylines, they overlap quite a bit.
Some online slots allow you to choose how many paylines to play and others have a fixed bet per spin.
Not all online slots have paylines as such – they may use ways to win, groups or other scoring systems.
In a ways to win slot, what you are looking for is sets of matching symbols on consecutive reels starting from the left, regardless of where they are positioned on each reel. You might say that they have no paylines, or all possible paylines; whichever way you look at it the stake is a fixed amount and there’s no opportunity to change the number of lines you play. A standard 5 x 3 reels array has 243 ways to win (e.g. the Microgaming classic Immortal Romance) but that’s just the beginning. Try Raging Rhino for 4096 ways or try a Megaways slot for a potent combination of ways to win and variable height reels yielding thousands or even tens of thousands of ways to win, changing every spin.
With this type of scoring system you win by getting groups of matching symbols that are horizontally or vertically adjacent to each other. Popularised by the NetEnt slot Aloha! Cluster Pays, variations of it are used in many other games including lots of titles by Play’N’Go.
Other scoring systems are still generally based on either lines or groups, but evolved or adapted for unusual play areas. For example:
- Finn and the Swirly Spin – any horizontal or vertical line of three or more of the same symbol anywhere on screen scores. That’s line based.
- Sweet Bonanza – 8 or more of the same symbol score, anywhere on screen, with no need for the symbols to be adjacent to each other. That’s group based.
The paytable is where you’ll be able to see how many paylines there are (if any) and how they are arranged, which combinations of symbols pay out, and how much they pay out. The payouts are specified in coins rather than actual amounts, to accommodate any size stake, any currency and any number of lines played – and this where the concept of coin size comes into play.
Coin Size & Spin Value
Coin size is the basic bet per line (assuming that the slot has paylines). On slots where the number of paylines to be played is user selectable it is equivalent to the bet per line, but on multiway and non conventional slots and those where all paylines must be played, the bet per spin or spin value will be a set number of coins shown on the screen. Siberian Storm for instance has 720 ways to win and the bet per spin fixed at 60 coins – so with a coin size of 1p you’d be betting 60p per spin and with a coin size of £1 you’d be betting £60 per spin.
The Super Bet feature was first seen in the Merlin’s Millions and Foxin’ Wins slots by NYX Gaming. It offers a way to make the slot more exciting by introducing an extra feature in return for a fixed extra bet per spin (on top of playing the maximum number of paylines). In Foxin’ Wins, playing Super Bet increases the number of fox cub wilds in the game and in Merlin’s Millions it increases the wild multiplier. This type of feature can also be seen in other slots such as IGT’s Western Belles, where you can pay extra to turn one of the reels wild. Yet another slot with this type of feature is Net Ent‘s manga themed slot Koi Princess; there it is called Bonus Bet and doubles the cost of a spin while increasing the chances of getting a bonus feature (as well as altering some of the bonus feature payouts in the player’s favour). In most cases, extra bet features just increase the variance and the entertainment value along with the cost per spin but sometimes they have an effect on the RTP as well (as in Merlin’s Millions where the 10x multiplier Superbet has a slightly higher RTP than the base game, and in Hotline where playing with all three hotlines enabled is more expensive but increases the RTP).
Slots with a gamble feature allow you to gamble the proceeds of a winning spin (or even the proceeds of an entire bonus round). It is usually a simple double-or-nothing gamble on whether the machine will turn over a red card or a black card, with a cap either on the number of times it can be done or on the maximum amount you can win. A few slots such as Microgaming’s Untamed series have a more sophisticated gamble feature that allows the players to adjust both the odds of the gamble and the amount of winnings to include in the gamble.
Many casinos specifically prohibit players from using the gamble feature on slot games while playing through a wagering requirement.
Slot Game Symbols
Regular symbols in a slot game score as detailed in the paytable, with some symbols scoring more than others (often much more). It’s common for low paying symbols to be relatively simple looking and higher scoring ones to be fancier. In many games the low paying symbols are inspired by playing cards regardless of the actual theme of the game; in Bonanza, for example, there’s 9,10,J,Q.K,A, then gems as higher paying symbols. In themed games with characters, the characters are normally the higher paying symbols and the props the lower.
There’s also a number of types of special symbol that may come up.
A wild symbol is one that can substitute for another symbol in a payline, group or whatever – so Q,Q,Wild would score as if it were Q,Q,Q. It is important to check the paytable as there are very often some symbols which the wild doesn’t substitute for (typically the scatter, bonus and jackpot symbols if the slot has them). Many slots have an additional feature attached to wilds (sometimes for the bonus round only); perhaps the most common of these is a multiplier for any winning combo of which it forms part. Other types of bonus feature involving a wild include:
- extra wilds on the reels
- random wilds that replace other symbols when the reels stop
- the stacked wild (where several wilds appear next to each other on one reel to form a stack)
- the expanding wild (which turns adjacent symbols wild as well)
- the wild reel (where the whole reel turns wild)
- the walking wild (which moves across the play area one reel at a time until it disappears off the side)
- the sticky wild (which remains in place for the next spin, for a free respin or even for the remainder of a bonus round)
There are some very popular slots that have fun gimmicks connected with wilds. Fluffy Favourites has a dancing pink elephant (in the sequel Fluffy Too it’s a twerking pink elephant) that doubles wins and triggers the free spins. And there’s the Starburst Wild, of course.
Scatter symbols pay regardless of location. Payouts for combinations of scatter symbols do not depend on groups, paylines or ways to win but are triggered if the required number of scatters appear anywhere on any of the reels. Very importantly, this means that if the bonus round in the slot you are playing is triggered by scatters, the chances of getting it remain the same whether you play 1 line, all the lines or somewhere in between. You won’t therefore, lose out on the potential entertainment value of the bonus round by choosing to play fewer paylines. However, in order to keep the RTP consistent the bonus round payouts are usually calculated as a multiple of the bet size on the triggering spin, so you’d win 20 times as much in the bonus round if you had been playing 20 lines than if you had been playing 1 line.
Games such as 9 Pots of Gold and Hyper Strike take scatters to the extreme, awarding payouts for up to 9 scatters.
Bonus symbols normally behave like scatters but trigger the bonus round (more of this later) instead of scoring. In some games, though, they are more like regular symbols in that they need to be lined up on a payline. For example, in Gonzo’s Quest Megaways the bonus symbols need to appear on consecutive reels, left to right, to trigger the free spins.
Bonus Coin symbols were popularised by Blueprint’s classic game Fishin’ Frenzy (and all its sequels and imitators). The fish symbols have monetary values on them but these only come into play in the bonus round, when they can be collected by the Fisherman symbol; in the base game they behave like plain fish.
Another type of bonus symbol is seen in Fluffy in Space, where 3 or more Nellie symbols are needed to trigger the feature and once they have, they remain in place and the aim is to collect as many more as possible in 3 spins (with no other symbols counting for the duration). Each time a Nellie is collected, the number of spins resets to 3 again. When the player runs out of respins, each Nellie reveals a multiplier payout.
This type of Hold and Respin bonus symbol also features in Playtech’s Fire Blaze Jackpot slots; they do nothing in the base game apart from trigger the bonus round if you collect enough of them.
Jackpot symbols award the jackpot, or give entry to a bonus round where you have the chance to win one of several differently sized jackpots (an example of this is seen in Age of the Gods, where you turn over coins until you collect a set of three symbols and win the jackpot that goes with that symbol).
Slot Games – Advanced features
Modern slot games are full of exciting gimmicks and here’s just a few of the most common:
A multiplier multiplies your payout – e.g a 3x multiplier gives you three times as much. This could be for the current spin, the next spin or as is common with bonus rounds, a set number of spins or the duration of the bonus round. Multipliers can be awarded by the appearance of a special symbol or by means of a multiplier meter. This contains a series of multipliers that are triggered by consecutive wins. Each winning spin causes the meter to move one space and applies the new higher multiplier to any winnings from the following spin. When the run of wins comes to an end the meter typically reverts to x1. Multiplier meters are often found in combination with tumbling reels type features, as in the NetEnt classic Gonzo’s Quest and its sequel Gonzo’s Quest Megaways.
Megaways slots often (but not always) feature a rising multiplier during the bonus round. It goes up by one with each winning cascade, remains until the end of the bonus round and has no upper limit.
Tumbling Reels / Exploding Wins
In this type of slot originally invented by IGT (Da Vinci Diamonds is the classic example) whenever there is a payout all the symbols that form part of a winning combo disappear, the other symbols drop down into the vacant spaces and new symbols tumble down from the top of the screen to fill the gaps. This continues for as long as winning combos are produced. Other slot providers have similar game engines but they have to be called something other than tumbling reels as only IGT can use that term. Gonzo’s Quest with its Avalanche feature is a classic (and very popular) example of this type of slot, and most Megaways slots also behave in this way. There’s also games such as Jack Hammer and Jack Hammer II which have a similar sort of gimmick but back to front (the winning symbols instead of the losing symbols stay in place for the re-spin).
A number of popular slots have a tumbling reels type feature in the bonus round only and these include Microgaming’s classic Immortal Romance where their version of the feature “Rolling Reels” appears in the “Michael” version of the bonus round.
Mega symbols are 2×2, 3×3 or even bigger, stretching across multiple reels as well as occupying multiple spaces on each. They can be part of the base game – as in the Gigablox series of games developed by Yggdrasil where the giant symbols cause the reels they are on to spin locked together – or part of a bonus feature.
Bonus Features and Bonus Rounds
Most slot games have at least one bonus feature or bonus round and many have several. The TED slot game by Blueprint, for example, has 6 different bonus features and 5 different bonus rounds.
A bonus feature is something that can happen in the game to enhance the result of a spin, for example by adding extra wild symbols to the reels. The Starburst Wild, which expands to cover a reel and locks in place for a re-spin, is a classic example of a bonus feature.
A bonus round is a special area of the game that can only be unlocked by getting a particular combination of symbols. It’s not unusual for slots to have several different bonus rounds: Fluffy Favourites has 2 bonus rounds, and Immortal Romance has 4 bonus rounds.
The most common type of bonus round consists of free spins, usually with some kind of an enhancement such as higher paying symbols on the reels, extra wilds or a multiplier.
Another form that bonus rounds can take is that of the pick me, where the player chooses from a selection of items on screen to reveal payouts, multipliers or entry to further bonus rounds; the Toybox bonus round in Fluffy Favourites is a classic example of this.
Yet another type of bonus round involves playing a game such as rolling (virtual) dice or spinning a bonus wheel, again to receive payouts, multipliers or entry to further bonus rounds – as in the Road To Riches bonus round in Rainbow Riches (where you spin the wheel to decide how many steps the leprechaun moves up the path) and the Bar Crawl bonus round in TED (which is essentially a board game).
Buy the Bonus Round
In a “buy the bonus round” slot you can pay a multiple of stake (usually quite a high one) to trigger the bonus round instantly. This was banned in the UK after the BTG game Extra Chilli made it possible not only to buy the bonus round, but instantly gamble it and lose it. Many subsequently released slot games have got round the ban by including a feature that isn’t a straightforward buy of the bonus round but has a comparable effect – here’s some of the ways how.
- Including a bonus round collection mechanism, so you collect symbols, coins or whatever as you play to trigger the bonus round when the collection is complete
- Including the facility to buy a feature where the bonus round is just one of several possible outcomes
- Extra bet that makes the bonus round more likely (but not certain) to be triggered
- Extra bet that enables a bonus feature on every spin as in Starburst XXXtreme and Fishin’ Frenzy Fortune Spins
Slot games – Progressive Jackpots
In a progressive jackpot slot, many or all the instances of the slot (or suite of slots) at different sites are networked together, and each time anyone plays the slot a portion of the bet for each spin is added to the central jackpot. The jackpot is started off at a certain amount and grows with every spin until someone, somewhere gets lucky and wins the lot – after which it is reset to the seed amount again. Examples of progressive slots that you’ll find at bingo sites are Clover Rollover (exclusively at Virtue Fusion sites) and the various instances of the progressive version of Fluffy Favourites. From time to time one hears of million pound plus sums won at bingo sites and invariably this will have been done via play on a progressive jackpot slot; the most well known instance of this is still the £5.8 million won at Butlers Bingo back in 2012 on the now defunct Dark Knight slot (which was then part of Microgaming’s Mega Moolah progressive jackpot network).
Something to watch out for when playing progressive jackpot slots is that there is often a relationship between how many lines are played at how much per line and the extent to which the player is eligible to win the jackpot. The Clover Rollover progressive jackpot, for instance, only pays out in full on a line bet of £5 – which amounts to £25 a spin. Trigger it on a 50p spin (10p line bet) and you’ll win just 2% of the headline amount. A more usual arrangement is that found with the IGT Megajackpots progressive. This can be won in full after any spin, but the chances of winning it increase with bet size and this is also the case with the Playtech online slots such as the Age of the Gods and Gladiator progressives as well as the Microgaming Mega Moolah network. Details of any such relationship can be found in the paytable or game help file.
Another type of progressive jackpot you will come across is the Must Drop Jackpot. Unlike normal progressive jackpots which just keep on getting bigger and bigger until someone wins, these progressive jackpots are guaranteed to drop either before reaching a set amount or within a specified time frame. The former reset to the seed value immediately after they drop but the latter don’t reset until the next time period starts; in other words, once a Red Tiger Daily Drop has been won it’s not possible for anyone to win the jackpot again until the following day.
Progressive jackpot slots are popular because of that minuscule chance of winning a huge amount, but they do tend to have a lower return to player, not only lower than other slots in general but also lower than the non-progressive version of the same slot. If you play the regular version of TED for a while and then switch to the Jackpot King version, for example, you’ll find that you win noticeably less often.
For further information about these slots and where to play them, read our guide to progressive jackpot slots.