With more than 1.08 million machines worldwide as of 2016, slots are the lifeblood of both the landbased and the online gaming industry. The first machine of this type was invented toward the end of the 19th century but a lot of things have changed with the introduction of the virtual reel.
The first game that used a video screen instead of mechanical reels was introduced in the mid-1970s and was called the Fortune Coin. Gamblers initially approached the new type of slot machine with suspicion for a variety of reasons.
For starters, the resolution was rather low so the imaging was far from impressive. These early video-screen machines lacked animation, audio effects, and bonus features, not to mention most spinners were not tech-savvy and distrusted the Random Number Generators that determined the spins’ outcomes. The absence of the physical reels caused many to believe the machines were rigged against the players.
The mid-1990s were a turning point in the history of the “one-armed bandits”. This is when the first video slots with bonus features exploded on the scene. In February 1997, manufacturer Silicon Gaming launched The Odyssey machine, a multi-game video slot that featured a larger-sized screen, several bonus features, and significantly improved animation.
The immense popularity of its successor, Reel ‘Em In by WMS Gaming (launched later in 1997), made game designers realize that video slots are the future of the constantly evolving gambling industry.
Soon after classic three-reels slots gave way to their improved cousins as the latter significantly advanced the entertainment value of slot machines. If you are yet to transition from classic to video slots, this article might be just the thing you need.
We explain the differences between the two types of games, the bonus features of video slots, and how betting on multiple lines works. Here you will also find several compelling reasons for and against playing multi-line video slots.
Multi-Line Slots' Bonus Features in Brief
Video slots would not have risen to such great popularity had it not been for the bonus features they are equipped with. In addition to the standard cash prizes players can collect from the paylines, they can trigger bonus events like free spins and different types of side games.
There are even slots where you can buy your way into these bonuses. Below, we lay out the key features you are likely to come across when playing multi-line video slots.
Wild Symbol 
Scatter Symbol 
Multiplier 
Cascading Reels 
Respins 
Cluster Pays 
Free Spins 
All Ways Slots 
Bonus Games Wild Symbol
The wild is a substitution symbol that can take the place of other symbols so that more winning combinations are formed on the paylines. The only exceptions are other special icons like those that trigger bonus games and the scatters. There are different types of substitution symbols, including expanding, sticky, floating, and stacked wilds, among others.
Scatter Symbol
The scatters are special because they can award payouts regardless of their positions on the screen. The player collects a prize as long as several scatters hit on neighboring reels. The scattered symbols are often the key to unlocking bonus events and free spins. This usually happens when three or more of these symbols land on the same round.
Multiplier
The multiplier boosts your winnings by a preset value, usually 2x, 3x, 4x or 5x although it is not unheard of to find video slots with more potent multipliers. For instance, if you win $10 during a bonus round where a 3x multiplier applies, you will collect $30 from the special feature.
Cascading Reels
In video slots with cascading reels, the symbols that form winning combinations “explode” and new ones fall in their places. This continues on subsequent winning spins until the feature is deactivated by a losing round.
Respins
The respin gives players additional chances of winning at no cost. Respins are sometimes triggered by wild symbols. When the wild appears on the reels, it causes them to respin on the house and this process continues until a loss occurs. In some video slots, this feature is not symbol-driven but occurs at random intervals instead.
Cluster Pays
Cluster Pays is a feature you will find mostly in video slots developed by NetEnt. These games lack traditional paylines. Instead, they pay out when the identical symbols form clusters. The symbols must be vertically or horizontally adjacent on the reels to award a cash prize. In NetEnt’s Aloha! Slot, you need a minimum of nine clustered symbols to receive a payout.
Free Spins
Free spins are a commonly available feature in most multi-line video slots. They are usually awarded when the player hits three or more scatters during a round. These are spins at no cost where the value of each free round is equal to the triggering bet’s amount. Multipliers are sometimes available during free spins to further boost your profits. In some games, the players can retrigger the free spins if they land the triggering symbol combination during the feature.
All Ways Slots
All Ways slots dispense with standard paylines. Instead, all symbols behave like scatters and award winning combinations when the matches occur in any position on adjacent reels. Games of this type usually give you 243, 720 or 1024 ways to win.
Bonus Games
Bonus games are the favorite feature of many video slot players and rightfully so. These come in all shapes and forms but some of the most common types include wheel-based and “pick-me” bonus games. This bonus event is usually triggered by a combination of symbols but it can occur randomly in some video slots. Either way, the player is guaranteed to lock in extra cash prizes at the end of the bonus event.
The Cost of Playing Multiple Paylines
The paylines have been an inseparable part of slots ever since this type of game first emerged. Early slots featured a single payline down the center of the reels. More recent three-reel slots award payouts on three horizontal and two diagonal win lines.
Multi-line games are a more elaborate but also a more expensive breed of slots. The player is expected to cover each payline with a bet. Otherwise, it will fail to produce a cash prize even if the winning symbols align.
The paylines of modern slots form all kinds of shapes. They would snake their way across the reels, zigzag, form V shapes or appear as chevrons. Video slots commonly have 20, 25, 30 or 40 paylines but this number varies greatly between games.
The availability of multiple paylines is beneficial to players because it increases their chances of aligning winning combinations. Furthermore, the same spin can produce wins on several paylines instead of just one.
With that said, the player is expected to post a wager on each active line which significantly increases the cost per spin. There are two types of paylines – fixed and adjustable. The latter give players the option to deactivate one or more of the paylines, which naturally decreases the games’ winning potential.
Slots with fixed paylines give you no such opportunity. You play all lines or none. This can be rather expensive for spinners on a limited budget, especially if the game uses a high minimum denomination for its coins. For example, if you play a slot with 30 fixed lines where the minimum coin value is $0.10, each spin will cost you $3.
From the perspective of casino operators, fixed paylines became a necessity when penny slots gained popularity in the early 2000s. With a minimum bet of $0.01 per spin, these machines were not as profitable for the house. This caused game designers to come up with the idea of the “forced bet” aka the fixed payline.
One such machine would not allow players to deactivate any of the available paylines. All they can do is choose how many coins to bet per spin. For example, the gaming controls panel on a slot with 20 fixed lines would feature buttons that read Bet 20, Bet 40, Bet 60, Bet 80, Bet 100, and so on. Bet 20 is the first bet level where you practically cover each of the 20 win lines with a coin. You spend two coins per line with the Bet 40 option and so on.
Many advanced slots have more than one bet level, i.e. you can wager multiple coins on each payline, usually up to ten. Such is the case in NetEnt’s Divine Fortune where you have 20 fixed lines, a minimum coin denomination of $0.01 and ten betting levels.
It makes sense that the higher number of win lines increases the hit frequency of slot machines. The trouble is it also lowers the average amount you win back on each payline.
You win some credits but lose the coins you have wagered on the lines that failed to produce winning combinations. Many spins would result in losses despite the machine declaring you have won.
When Losses Are Disguised as Wins 
Multi-Line Slots and Random Number Generators 
Return Percentages and Volatility in Multi-Line Slots 
Video Slots without Paylines When Losses Are Disguised as Wins
The trouble with multi-line slots is that many losing spins are disguised as wins. Here is an example of how this happens. You play a slot with 20 active paylines and cover each line with a coin, for a total bet of 20 coins. The reels are weighted so that low-paying combinations occur more frequently than the top payers.
Suppose, for instance, the slot in question returns 6 coins for combinations of three Q and 7 coins for three J. The two low-paying combinations hit on line 12 and line 20 at the end of a spin. You “win” a total of 13 coins with your 20-coin bet. Essentially, you are 7 credits down for this round.
What’s troubling here is the effect losses disguised as wins have on the psychology of the players. Multi-line slot machines behave as if the player has hit a big win instead of losing. The overall loss is “masked” by celebratory sounds and animations.
Worst of all, this behavior of the machines influences the players and urges them to continue betting. This causes some spinners to overestimate the winnings they have generated during a betting session and underestimate their losses.
On a side note, players respond similarly when they experience near misses on classic three-reel slots. It turns out nearly winning and actually winning affect their brains in a rather similar manner.
The long and the short of it is losses disguised as wins encourage spinners to bet on more than one line, allowing gaming designers to create slots that award payouts on almost every spin. Despite the higher hit frequency, the proportion of the money paid back is often less than the player’s overall wager.
Multi-Line Slots and Random Number Generators
The driving force behind advanced multi-line slots is the Random Number Generator (RNG). This technology is used in both online and brick-and-mortar casinos. It guarantees the outcome of each spin is entirely independent from previous results.
The RNG starts to generate thousands of random numbers per second the moment the slot machine is turned on. The outcome of the round is determined in the very millisecond the player hits the spin button. The reels begin to spin solely for aesthetics and authenticity purposes.
The software chooses a random number for each of the five reels. Each randomly generated number corresponds to a specific stop. The machine tells the reels to halt on the stops picked by the RNG. Many of them contain blank spaces and low-value symbols, which explains why top-paying combinations occur less frequently.
Modern multi-line machines do not even need physical reels to award payouts. You could just place your wager and the game could immediately tell you whether you win and if so, how much. The reels are there just for show to tell the player what result the game’s software has already chosen.
As previously explained, all slots have their reels weighted to guarantee the casino turns a profit over the long run. Physical reels are not big enough to hold a larger number of symbols. The RNG uses virtual reels where more symbols can be mapped.
The positions of the symbols on the virtual reels always remain the same. The symbols are permanently mapped in place, making sure the slot arrives at its expected theoretical return percentage.
There are tons of strategies for sale online that supposedly enable players to beat the slots. Unfortunately, these are all ineffective because it is impossible to predict randomly generated results.
Return Percentages and Volatility in Multi-Line Slots
All video slots are preprogrammed with a specific theoretical return percentage. This is the amount paid back to players over the long term. For example, a game with a payback percentage of 97% is expected to return $0.97 for every dollar wagered on it.
Payback percentages are cumulative and are distributed between all players who bet on a specific slot. Great fluctuations can be observed in the short term, with spinners losing or winning big within a dozen or so spins.
No slot game in the world offers a theoretical return of 100%. All machines are programmed to return less money than players collectively wager. If you play long enough, you are guaranteed to come out in the red. Because of this, reel spinners are always recommended to keep their sessions short and collect their profits as soon as they hit a decent win.
Machines with higher minimum denomination normally have better payback percentages. For example, a slot that uses a minimum betting unit of $1 would pay better than a $0.50 game, which pays better than a $0.25 game, and so on.
This is achieved by improving the paytables of high-denomination slots and mapping more random numbers onto the high-value symbols. The theoretical return percentage is almost always the same no matter how many coins you wager per payline.
Some players are left with the impression they win more frequently when they bet the minimum and less frequently when playing the maximum. It causes them to believe the RNG is programmed to pay out more often on minimum bets and less often with maximum bets.
This misconception stems from the fact such players are working with very small sample size. The results would balance out with extended play and more observation. Betting patterns are irrelevant to the Random Number Generator – it has no way of knowing the size of your bet. Bet size has no impact on the random numbers and the probability of alike symbols lining up on the paylines.
The hit frequency of a slot tells you how volatile the game is. Slot volatility is a measurement of the distribution of outcomes within a specific period. It also denotes the level of risk involved in the game, i.e. how likely you are to deplete your bankroll when playing the slot.
Games with low volatility are less risky and have higher hit frequencies but the payouts they reward you with are lower. In contrast, video slots with high volatility are riskier because winning combinations occur less often. Such games compensate with better payouts.
Provided that high-value combinations yield big enough returns, a slot with high volatility might have a better return percentage than a low-volatility game where most of the returns result from low-paying symbols.
Video Slots without Paylines
Most video slots are equipped with scatters which pay whenever three or more symbols land anywhere on neighboring reels. More often than not the matches should occur from left to right although there are games that pay both ways. It is irrelevant whether the symbols appear in top, middle or bottom positions on the reels.
Some game developers have taken this concept to a whole new level, creating video slots where all symbols behave like scatters. Such games are entirely devoid of paylines. They have many winning combinations but low dispersion, which means wins occur more often but the payouts they award are lower.
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Reasons Against Playing Multi-Line Slots
Despite being the most played games on the casino floor, multi-line video slots have a bad reputation within the gambling community, with many longtime casino goers avoiding them at all cost. Of course, it all comes down to personal preferences and perspective but the three downsides listed below are valid enough reasons to take your action elsewhere.
Poor Odds and High House Edge 
Inconsistent Odds, Payouts, and House Edge for Identical Slot Machines 
No Strategy Can Help You Win Consistently Poor Odds and High House Edge
The gambling industry relies on a concept called the house edge, which is a measurement of the statistical long-term advantage the house extracts from a particular bet or game. Video slots offer poor odds and yield higher house edges than most of the other casino games.
The average house advantage here ranges between 6% and 8% based on factors like payline number, minimum coin denomination, bonus games, progressive and fixed jackpots. The house edge is the flip side of the theoretical payback percentage, which is also influenced by the above-listed factors.
To put these percentages in perspective, even notoriously bad games like double-zero roulette offer you better odds and a lower house edge (5.26%) than many video slots. Card games like blackjack are your best bet since you can reduce the built-in casino advantage to around 0.5% with accurate basic strategy.
If you are averse to the idea of playing with other patrons against a dealer, you should try video poker machines with more liberal paytables. These can even give you a thin advantage over the house.
Inconsistent Odds, Payouts, and House Edge for Identical Slot Machines
Another trouble with slots is there is no standardization of their odds, house edge, and payout percentages. With standard random games like roulette, craps, and baccarat, you always know what house advantage and odds you are up against.
This is not the case with slots where the odds and the payback percentages might vary greatly even on identical games. A player might deplete their entire session bankroll in less than thirty minutes on a given slot only to find the same machine in another casino pays and plays much differently than the first one.
Data compiled by major regulatory authorities like the Nevada Gaming Control Board (NGCB) suggests slots in Downtown Las Vegas offer better payout percentages than those of similar machines on the Strip.
The results of a survey conducted by the NGCB indicate that slots on the Strip retain as much as 7.88% of all wagered money while the same games in Downtown Las Vegas yield a lower house advantage of 7.13%.
These discrepancies result from the fact most game designers give casinos a choice from a range of payback options. The same machine is often available with theoretical returns of 89%, 92% or 94%, for example. It is up to the casino to choose which option to purchase. This information is not posted on the machines, making it impossible for players to shop around for the best-paying slots.
No Strategy Can Help You Win Consistently
Even if players know the payout percentages of the slots they play, this information cannot help them overturn or reduce the built-in house edge they are fighting. The results are picked based on an entirely random principle. Subsequent outcomes are fully independent of previous results.
Respectively, no strategy can help you win consistently in the long term. Certain approaches enable you to extend your playing session and lose money at a slower rate but the odds remain stacked against you. If you play long enough, you will inevitably end up on the losing end.
Reasons to Try Multi-Line Slots
Despite their downsides, video slots remain the most played casino game of all time. Now that we have outlined the main disadvantages associated with multi-line games, let’s have a look at some of the most compelling reasons to try them.
Their Simplicity Renders Them Suitable for All Experience Levels 
Casinos Offer a Broad Choice of Options to Slot Players 
Video Slots Are Broadly Available Their Simplicity Renders Them Suitable for All Experience Levels
This is perhaps the most compelling factor behind the immense popularity slots enjoy. Many novice gamblers are intimidated by the table games where things tend to get rather hectic and confusing, especially during busy hours.
This is not the case with slots which offer a solitary experience to the bettor. When at a landbased casino, you sit down at the machine by yourself and can play at your own pace, without dealers urging you to place your bets and annoying table mates pestering you with unsolicited advice.
Additionally, you do not need much in terms of teaching to understand how slots play. The intuitive interface and gaming controls make it possible for anyone to learn in under a minute. You simply post a bet, press the spin button, and wait for the outcome. If you are lucky, you collect a payout. If not, you keep your fingers crossed that the next spin will produce a win.
Casinos Offer a Broad Choice of Options to Slot Players
One particularly appealing aspect of slots, especially if you play online, is the vast choice of games you face. Many web-based gambling operators offer such immense collections that it would take you forever to try them all.
The games are usually structured in different categories based on the theme, payline number, bonus events, and even volatility. New titles are regularly released, often boasting improved and unique features. Software developers are constantly looking to better the experience of reel spinners, introducing newer and more advanced games.
Video Slots Are Broadly Available
Finally, we arrive at the topic of availability. The tables at landbased casinos are often overcrowded but you will experience no such issue with slots, especially at larger gambling venues where there are hundreds of multi-line machines.
Things are even better if you play online where there is no limit on the number of spinners who can join and play the same slot simultaneously. This gives you round-the-clock access to your favorite games at all times, not to mention you have the option to try the new releases for free before you risk your hard-earned money.