Online Casino Slots (A Guide to Reviews and How to Read Them)

The internet gambling industry is more dedicated to online casino slots than practically any other kind of game. For one thing, you’ll find more of these kinds of games than any other kind of gambling game online.

You’ll find plenty of sites offering online casino slots reviews. You’ll see plenty of people claim that their online slots guide is better than any other. But not all of these sites and the people behind them have your best interest at heart.

Most of these pages aggressively promote online casinos. There’s nothing wrong with that, but I hope to offer you more than just a page shilling online casinos. I want you to be an educated gambler. And I don’t want you to get taken by some of the information sites on the internet who offer little more than advertisements.

So one of my goals with this post is to show you a little bit of the other side of the industry. The more you understand about how the business works, the more educated an opinion you can have about the various slots guides on the internet.

How the Online Casino Slots Business Works

The first thing you need to know about online casino slots is that they are, for the most part, fair games. They’re not rigged. Online casinos don’t need to cheat.

Here’s why:

Online casino slots work almost exactly like slot machines in traditional casinos. A random number generator powers the results you see. That’s just a fancy name for a computer program which cycles through thousands of numbers every second.

Each of those numbers is keyed to a specific result on the reels. When you press the spin button, the result is determined long before the reels stop spinning.

The casinos make their profits by paying off your bets at less than the odds of winning.

For example, if you have a 100 to 1 chance of winning, and the payout averages 95 to 1, the casino profits in the long run because of the discrepancy.

In the short run, you can, of course, wind up winning some money.

But the way the math behind the game works, the longer you play, the likelier it is that you’ll see actual results similar to the mathematical predictions.

The games don’t know that you’re ahead or behind, though. They don’t modify their results based on how you’re doing. Every spin of the reels is an independent event.

How Online Casino Slots Review Sites Make Their Money

So it’s clear how online casinos make their money from online slots.

But how about sites like this one?

Where do we get our money?

The answer isn’t complicated.

Online casinos are lucrative, and an online casino player is worth a lot of money to the casino. An average gambler is worth at least $1000 to the casino over the life of the player–maybe more.

As you can imagine, this makes competition for customers fierce.

And one of the ways online casinos market themselves is through their affiliate program.

There’s nothing wrong with an affiliate program, by the way. It’s just good to know how it works.

Basically, the casinos pay commissions to website owners who refer customers their way. The most common commission structure in such a deal is called a “revshare agreement”.

If you sign up at a casino through the link in an online casino slots review, the URL you’re referred to includes a specific code. That way the casino knows who referred that player.

When that player generates revenue for the casino–by losing money playing slots, for example–the referrer gets a percentage of those losses.

That percentage varies according to the agreement with the casino.

This percentage might be as low as 10% or as high as 45%. The arrangements vary based on how much traffic the affiliate refers to the program.

What Does This Mean for a Slot Machine Player?

In terms of gameplay experience or payback percentage, none of the stuff about referrals and revshare matters to the average player. The gameplay experience at the casino is the same regardless of how you got to the casino.

In terms of how trustworthy, accurate, and informational the content on a website is, this stuff matters. Since the publishers of these website have a significant financial interest in whether you sign up, some of the information might be biased.

This doesn’t mean that all online casino slots reviews are nothing more than advertisements for online casinos. It does mean that some of them are, though.

It also means that some of these reviews might be a little more positive than you’d expect from a writer who’s truly impartial.

That’s all  good if you know beforehand what you’re reading and why it was written the way it was.

It’s not so great if you’re unaware of that aspect of how the business works.

What Do Most Online Casino Slots Guides Offer?

Most online casino slots guides offer reviews of online casino software packages. They usually feature reviews of specific games, too. And they invariably include links to online casinos where you can play the games.

One aspect of these reviews I’d take with a grain of salt is any claim about the payback percentage for a specific game. Some online casinos and software providers publish their payback percentage information. But most don’t.

Any estimates of payback percentages should be considered–at best–an estimate.

That’s one of the problems with slot machines in general as far as I’m concerned.

The payback percentage can’t be calculated.

To calculate the payback percentage for a gambling machine, you need 2 pieces of information:

  1. The payouts for all the possible winning combinations
  2. The probability of getting each of those possible winning combinations

With an online slot machine game, you have a pay table listing the payouts for the winning combinations.

But you have no way of knowing what the probability of getting a winning combination is.

The symbols are programmed to turn up a certain percentage of the time. But that probability can vary from symbol to symbol. A cherry symbol might be programmed to show up 10% of the time, while an orange might show up 20% of the time, and an apply, 5% of the time.

Without that information, you can’t calculate the payback percentage.

One Way You Could Estimate a Payback Percentage for an Online Casino Slots Game

Another  way to estimate a payback percentage for an online casino slots game would be to keep detailed records of your results and extrapolate that.

The first piece of information you’d need to do that would be how much money you’d put into action on that game.

Here’s an example:

You decide to run a test on Cashville slot machines. You’re betting a penny per line on 20 lines, so you’re putting 20 cents into action every time you spin the reels.

Make 1000 spins, and you’ve put $200 into action.

The next piece of information you need is how much money you won playing.

In the example above, let’s assume that you won $180.

You divide the amount you’ve been paid back by the amount you wagered to get the actual payback percentage for that session.

$180/$200 = 90%

The Importance of Lots of Data

The more data you have available, the more accurate your estimate will become. But keep in mind that a slot machine’s payback percentage is meaningless in the short run.

Using Cashville as an example again, let’s look at a tiny sample size–1 bet.

You bet 20 cents, and you win 200 coins (or $4).

The payback percentage for that single spin was $4/$0.20, or 2000%!

That’s obviously not the long term expected return for the game. You’d need to clock thousands of spin, maybe tens of thousands, before you had anything like a reliable estimate.

Now here’s a bit of common sense for you:

Do you think that the writer who created the slot machine review you read clocked thousands of spins before writing the review?

Probably not.

So any payback percentage number they come up with is just a ruse to make their review look more accurate.

I could be wrong about this in some instances. But I’m certain that some webmasters just make up a number that sounds good.

Specific facts and figures create more confidence in a product, which increases conversion rates. And you already know what that means, because I’ve explained how the business works.

Online Casino Slots Software and Games

Most online casino slots guides organize their reviews of the available games by the name of the slot machine provider. That’s the company which programs the software running on the casino. Most online casinos don’t have their own proprietary software; they lease a program for another company.

Some of the companies providing online slot machines include:

  • 3Dice
  • Amaya
  • Arrow’s Edge
  • Bally
  • Betsoft
  • Booming Games
  • Cryptologic
  • EGT
  • Foxium
  • Gamesys
  • Grand Virtual
  • Habanero
  • IGT
  • Iron Dog Studios
  • Microgaming
  • NetEnt
  • Nextgen Gaming
  • Nuworks
  • Octopus Gaming
  • Parlay Games
  • Party Gaming
  • Play N Go
  • Playtech
  • Pragmatic Play
  • RealTime Gaming
  • Red Rake
  • Red Tiger
  • Rival
  • Slotland
  • Spinomenal
  • Topgame
  • Vig
  • WGS Technology
  • Yggdrasil

That might seem like a comprehensive list, because there’s a lot of names on it. But it barely scratches the surface.

What Can You Learn from Most Online Casino Slots Reviews?

Most online casino slots reviews include some of the basic information about the game in question. This includes:

  • The number of reels
  • The number of paylines
  • The bet ranges
  • The symbols and theme
  • Bonus features

The Number of Reels

Most slot machine games have either 3 reels or 5 reels. 3-reel slots games tend to look like classic slot machines. 5-reel slots games tend to be more like video games.

These are analogous to the games in traditional casinos. Even the traditional-looking, mechanical slots in brick and mortar casinos use a random number generator these days. Mechanical slot machines using gears and springs are only available in museums these days.

In a brick and mortar casino, boring 3-reel slots usually have a higher payback percentage than the 5-reel games. This might or might no be true at online casinos. The bonus features in video slots with 5 reels probably cost a certain amount of money in payback percentage.

The Number of Paylines

On the most basic of slot machines, you have a single payline. That’s the horizontal line across the center of the 3 reels. You can usually see the symbols on the reels above and below that reel. Those could be 2 additional paylines.

Other paylines can be drawn using various shapes. The paylines that you can activate are displayed on the slot machine game’s pay table, usually.

Every payline is treated as a separate bet.

The Bet Ranges

Some slot machine games are available for as little as a penny per payline per spin. But you can find high roller games where you can bet $100 (or more) per spin.

Any detailed online slots review will include the stakes available for the game.

The Symbols and Pictures

Any reasonable slot machine review will at least include a description of some of the symbols used in the game. They should also include information about wild symbols and scatter symbols.

Wild symbols count as any symbol you’d need to complete a winning combination. A wild symbol on a slot machine is analogous to a joker in a deck of cards.

A scatter symbol is a symbol that can trigger a payout no matter where it is on the payline. These increase the chance of a win.

Really detailed slot machine reviews include complete list of symbols and what their combinations pay off at.

Bonus Features

Modern slot machine games, especially those found online, usually offer bonus features. These often take the form of free spins or bonus games where you can win extra money.

These bonus games can be as simple as guessing whether the next playing card will be black or red. The bonus prize for that one is usually doubling your money.

They can be complicated, too. I’ve seen games where you got to play virtual video games and shoot aliens for prize money.


Online casino slots reviews and guides can be entertaining. Just keep in mind the motives of the people writing and publishing these pages. They have a goal–to get you to sign up at the online casino.

This doesn’t mean they’re lying or publishing inaccurate information. It just means that the information might be more biased than you expect.

Forewarned is forearmed.

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