The purpose of slot machines is not to enrich a player for a long period. Quite the contrary. Therefore, the game of slot machines should be considered only as entertainment, but not as a stable income in any way. Of course, every player wants for entertainment the slot machine game which “gives” more than “takes”. So that the charm of a possible big win never goes away.

Flame of Olympus slot machine $5 bet, 15 spin bonus round, Rio Las Vegas, March 2013 - Duration: 3:12. Sphinx 3D slot machine bonus round, Palazzo Las Vegas July 2014 - Duration: 6:09.

Players choose slot machines, guided by various criteria. Today we will try to group all the parameters according to the degree of importance and we hope that our article will help many players to choose the most suitable slot machine. Despite the different views of the players, the machine obtained according to our criteria will have to satisfy their requirements.
Criterion 1. Developer of the slot machine
Players do not always pay attention to the developer of the slot machine. And it doesn’t matter if it’s best free slots with bonus rounds or real money version of the classic slots online. Only professionals who know a lot about games and manufacturing companies do it. But this is a very important factor in choosing a game or casino as well. Developments by unknown or no name game makers often cannot provide either a high percentage of return or a stable issue of funds. The parameters of such unprotected machines in reality are easy to change, and casino owners will explain the malfunctions in the operation by software failures.
With virtual casinos the same situation. If the browser program or the stationary version of the casino has an open code, it can be used for fraudulent purposes: to reduce the percentage of winning and the amount of users’ jackpots.
That's why choosing a machine, you need to analyze the list of manufacturers and consider the development of only the most famous and reliable. Bitcasino, Playtech, Microgaming, and Vegas Industry, have very high authority around the world. Providers of Asocial Gaming, 1x2 Gaming could not gain the same excellent reputation due to non-compliance with license standards or refusal to pass an audit of honesty.
Criterion 2. Formation of lines
Most often, gaming machines with a small number of reels and lines are the most greedy and boring. But even slots with 50 lines will not bring the desired satisfaction: even if winnings fall out often, the payout amount in most cases will not be able to cover even the amount of the initial bet.

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Therefore, before playing for real money, we advise you to study the principles of pay line layout. You can do this by opening the payout table Info or Paytable. One-sided machines, when winning combinations add up in only one direction (from left to right) in the long run, bring much less money than “two-sided”. The best option to play in such slots is to use no more than three lines. Or use “two-sided” slot machines with bonus rounds only.
Criterion 3. RTP of the machine
Each machine has different RTP (return to player) indicators. To learn how to calculate them, you need to study the coefficients in the Info tab. The maximum multiplication of machines with low RTP is 2000-3000, and with minimal combinations it can decrease to 0.5 - 1.0 of the initial bet amount. With very high odds (10,000 - 100,000) in the slots, you need to be careful, because winning in such a machine will make you wait a long time. The frequency of winnings in such slots is reduced due to the fact that large sums of bets will be covered in a long run.

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This means that the slot with the maximum multiplication of 5000 - 10000, with the number of possible prize combinations of more than 30, will become the most suitable. If the prize combinations add only two symbols, such a slot machine is as close as possible to the standard in terms of RTP.

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Criterion 4. Bonus rounds in free slots and slots for real money
We exclude from our list slot machines in which there are no free bonus round games. Most often these are standard 3-drum machines, and sometimes 5-drum machines. It is very important for the online slots game to have free bonus rounds. The most effective slot machines will be those that offer players a conditionally infinite bonus game (Fruit Cocktail for example), or activate a certain number of free spins (like in Magic Book slot).
If the slot has free bonus round games, then it implies an additional increase in the total winnings. Of course, it will depend on the number of Scatter symbols dropped out on the reels of the game. In the payout table of each slot with bonus rounds you can compare multiplication rates and the number of free spins, understand the concept of bonus spins. There are such varieties of bonus games where the reels are completely replaced by a wild symbol, significantly increasing winnings and multiplier of the initial bet made by the player.
Criterion 5. The presence of a wild symbol

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The presence of this symbol in the machine is not just important, it is vital. Wild helps players to build prize combinations and, thus, increases the number of wins. The payout table will show you the probability of a wild symbol falling out on the reels. It is directly proportional to the growth of the initial bet and sometimes can be compared to the jackpot.
Criterion 6. Risk game

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Today, almost every slot machine has a doubling game bonus game, which is offered to the player after winning Spin. But doubling games are different. The most effective is the game in which you need to get a higher value card that the dealer’s card. It is more profitable than guessing “black-red” because it gives more chances to win.

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So what is the perfect slot machine?
Let's recall the above criteria and determine for ourselves a truly perfect slot machine. First of all, it should be the development of a reputable manufacturer, be multi-linear and involve various free bonus rounds. Best of all, if the device has an average RTP and provides the possibility of creating prize combinations from right to left and vice versa.