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Online and Random

How does the RNG work when you’re playing slots online?

By Frank Legato


OnlineSlotsI can’t count the times I’ve used this column to explain how the random number generator in a slot machine works. It’s one of the most frequently asked questions from our readers, so we’ve devoted a lot of space to it over the years.

These days, though, slot players have another option besides physical slot machines when it comes to playing slots: the internet casino. So far, you can only legally play slots for money online in the United States while you are physically in either New Jersey or Delaware. (Nevada has some online gambling as well, but that is limited to poker and sports betting at the moment.) However, the conventional wisdom holds that this will not be the case much longer, and if you’re in Canada or Europe, online slot play is already a commonplace option.

As for-money Internet gaming continues to spread across the U.S., players also can play slots for fun on a variety of social sites like Facebook.

All of this begs the same question so many of you have asked with respect to the RNG: How do these online systems choose the results on a slot game? The answer: exactly the same way as the slot machine in your favorite casino.

Just to review, the RNG is a utility software program burned into the game chip of each physical slot machine. Its function is, as the name says, to generate numbers. In a slot, the program is rapidly generating numbers at random from a set of numbers which each correspond to a result on the physical reels. The slot programmer gives a number to each symbol or blank on the map of the physical reels, and then duplicates the numbers to create a theoretical payback percentage.

Low-paying symbols or blanks each get a lot of numbers; high-paying symbols, including those making up the top jackpot, get only a few or one number assigned to them. The RNG mixes them all up and generates numbers at random, freezing the combination of numbers generated the nanosecond that a spin is initiated. It then communicates the combination to the slot’s computer, which tells the reels (or video reels) where to stop. It all happens in an instant.

Online casinos generate results in the same manner. The main difference is that the random number generator program is housed on a central computer server. The player logs into that server to play the games. When a game is selected, the server loads the so-called “front end” of the game code—the graphics, the images, the game features—and presents the game to the player.

“When the player hits the ‘play’ button on a game, the device (his PC, mobile phone or tablet) talks to the connected server,” explains Mike Halvorson Jr., chief development officer for online gaming content supplier Spin Games LLC. “Each game has a separate, distinct usage of the central RNG to power the results that drive the game, but it is all done on the server.”

Halvorson explains that once a player is logged into a server and selects a game from the “lobby,” he is playing the game directly on the server, not on his computer. “The RNG is the same for each user, but it is a different instance, and it powers the results of each game,” he says. “Once the device gets back a result of an action from the server, the player will see an action like a reel spin, bingo ball draw, wins, losses etc.

“Think of the device as a car with no gas. Each result from the server powers that car to move just a little.”

The RNG program on the central server of an online casino multi-tasks—it can cycle through individual game results on individual games “for millions of concurrent users, with all of those instances working at the same time,” says Halvorson.

When you play a slot game on an Internet casino, you are accessing a game program that is identical to the same game in a land-based casino. Penny versions of a particular game will carry the same payback percentage and hit frequency as their casino counterparts; same thing for quarters, dollars and other denominations. As in land-based casinos, the higher denominations are likely to carry higher payback percentages.

As far as the results, the same principles apply: The results are random, they are unpredictable, and whether you win or lose is based purely on chance.

The only other differences? You won’t get to ride a Motion Chair or see other big, flashy physical displays. And no cocktail servers.

See you in the casino! •


Quick Tip: Link online to land-based

The number of online casinos in the U.S. is currently limited to New Jersey and Delaware, but each online site in each state is linked to a physical casino. There are links to online sites at each casino website in these two states.

But players do have choices, and as you do with physical or “land-based” casinos, as they are called in the trade, you can choose the one with the best deals. The nascent online casino sites are inexorably linked to their land-based hosts, and the idea, for the operators, is to use the online sites to generate traffic into their physical gaming halls. At Caesars online sites, for example, you will be able to earn points in the Total Rewards player’s club by playing at online casinos, and redeem them at the physical casinos.

The online casinos will offer bonuses that can be used in the physical casino. Some have a better variety of games than others, but all of them offer promotions. The best course of action is to shop around. Pick the online site that will give you the best awards when you do return to the casino.

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