Last update: 16th October 2019
Almost without exception (the exception was Tombola but even they have their own slot type games now in the Tombola Arcade), online bingo sites also offer an array of online slot machines and this can be bewildering if you’ve never played slots before. Modern online slots are a far cry indeed from the mechanical fruit machines of the last century. These were also known as one armed bandits – the one arm referring to the lever on the side that was pulled to make the reels spin, and bandit because they took your money! One armed bandits typically had three mechanically operated reels with symbols on them including fruits, and to win you had to line up three of a kind across the middle.
As well as offering multiple paylines, bonus features 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%.
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 in this instance and it could be much higher or much lower. However much cash you have left after playing through the £100 you deposited, if you continue to play you will now be playing with money that has already been through the slot once – and that RTP of 95% applies every time you play it through. It’s like compound interest in reverse! 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).
The reels have the symbols on them and spin vertically when you press play. Classic fruit machines had three mechanical reels but modern slots usually have 5. Whether you come across a modern slot machine online or at a bricks and mortar casino, the reels will be virtual rather than mechanical with the stop position determined by a random number generator. This means that each reel, in effect, can contain hundreds of symbols (many more than could be accommodated within the confines of a physical machine) and this in turn means that the probability of a symbol that only appears once on the virtual reel coming up, is much lower than the probability of a symbol that only appears once on the mechanical reel coming up. This sounds bad for players on the face of it but actually it isn’t. 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 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 on the mechanical reels is therefore going to be triggered more than 2000 times as frequently 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.
5 x 3 – 5 reels with 3 positions visible on each reel – is the standard arrangement of reels found on a great many online slots. It is not ubiquitous though as there are some with 5 x 4 or 6 x 4, some with completely bizarre looking arrangements involving multiple sets of reels, triangular or hexagonal arrays and even some that don’t appear to have reels at all but instead resemble a Candy Crush board. Even where there is a conventional arrangement the reels may not look like spinning reels but like cascading gemstones or waves crashing on a beach, for instance.
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).
In the case of the one armed bandit there would be just one payline, running across the centre of the reels, and it would be the symbols that appeared in those three positions that determined whether and how much you had won. With online slots 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 on reels 1 and 2 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. Multiway slots such as Immortal Romance (243 way, by Microgaming), Siberian Storm (Multiway Xtra by IGT with 720 ways to win) and Raging Rhino (Any Way by Williams with 4096 ways to win) pay for any combination of 3, 4 or 5 of a kind on adjacent reels (but they still have to start on reel 1 unless they pay both ways). There’s also a few weird and wacky slots such as IGT’s Bubble Craze, NetEnt’s Finn and the Swirly Spins and many gamesby Play’N’Go that score in a different way entirely.
The paytable is where you’ll be able to see how many paylines there are and how they run, 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.
This is the basic bet. 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 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.
A bonus round is a special part of the game that can only be unlocked by getting a particular combination of symbols. Not all slots have bonus rounds – Starburst is a notable example of one that doesn’t – and the ones that do have bonus rounds often have several different bonus rounds – Fluffy Favourites is one of these, with two bonus rounds, and TED has a massive 5 bonus rounds. The most common type of bonus round consists of free spins, usually with some kind of a bonus 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. The final type of bonus round involves carrying out some luck based activity 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).
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 Net Ent classic Gonzo’s Quest.
A wild symbol is one that can substitute for another symbol in a payline – so Q,Q,Wild would score as Q,Q,Q. It is important to check the paytable as there are very often some symbols which are excluded (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 the stacked wild (where several wilds appear adjacently 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) and 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 a twerking pink elephant) that doubles wins and triggers the free spins. Starburst has an expanding wild that covers a whole reel.
Scatters are a special type of symbol. Payouts for combinations of scatter symbols do not depend on paylines 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 so you aren’t losing out on the potential entertainment value of the bonus round by playing 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.
In this type of slot invented by IGT (Da Vinci Diamonds is the classic example) when there is a payout all the symbols that form part of a winning combo disappear 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 is a classic (and very popular) example of this type of slot, while the Jack Hammer games 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). There’s also a number of popular slots that have this type of feature in the bonus round only and these include Microgaming’s classic Immortal Romance where it appears in the “Michael” version of the bonus round.
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.
The Super Bet feature was first seen in the Merlin’s Millions and Foxin’ Wins slots by NYX Gaming. Basically 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). Generally 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).
In a progressive jackpot slot, many or all the instances of the slot (or group 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 at Virtue Fusion sites and Millionaire Genie at 888/Cassava sites – and, of course, 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 (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 Age of the Gods and Gladiator progressives and the Microgaming Mega Moolah network. Details of any such relationship can be found in the paytable.
Progressive jackpot slots also tend to have a lower return to player than both other slots in general and the non-progressive version of the same slot.
For further information about these slots and where to play them, read our guide to progressive jackpot slots.
Variance, or volatility, is a measure of how much the slot is likely to deviate from the average return to player in one play session by one player – and how many spins are 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 with a very high paying and rather rare bonus round but not much of a payout during normal play has high variance – do 100 spins on that 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 is not so easy to find out the variance. Some slots such as Dead or Alive by Net Ent (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 be a while before the variance is reported. A close inspection of the paytable can yield clues; if the 5 of a kind payouts are relatively high and/or the bonus round is a particularly lucrative looking one, then they represent fairly rare events.
Many players prefer the excitement of a high variance slot but do remember that although it is possible to score a massive 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. The aforementioned Dead or Alive, for example, is often excluded.
All of the bingo sites we feature also have a selection of slot games, but if you’re after the biggest choice of slots combined with a slot focused welcome offer, there’s a great range of sites and offers on our Top 50 UK Slot Sites page.
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