Slot machines are the most profitable part of a U.S. casino. From Las Vegas to Atlantic City, slot machines take up more space than any other casino game. Online slots work the same way. If an online casino features 300 games, 250 of those games will be online slots. When playing with Android or iPhone devices, mobile slots revenues work the same way.

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Guide to Online Slots

Our guide to online slots covers both online and mobile slot games, including traditional land-based slot design companies like IGT and Bally slot machines. We also cover the biggest names of the online slots era, such as Microgaming, RTG and NetEnt. This page discusses 3-reel classics, 5-reel video slots, licensed slots, progressive jackpots, and 3D online slots.

Though the world of slot machines is vast, it doesn’t take long to figure out how online slots work and how to play online slots. If you have any questions, feel free to send us an email or read our slots FAQ page, which answers over 120 questions about the online and mobile slots industry in 2021.

Online Slots for Real Money

Beginners should read our online slots guide about the types of online slots they’ll encounter. New bettors searching for online slot tips should look at the strategy articles below. Beyond that, players should always know the odds when they play slots online. Learn concepts like variance and the house edge, along with other tips for picking the best online slots.

Top 5 Online Slot Software Developers

Online slot software has more variety than any other casino game online. Some casinos offer Vegas-style online slots, while others include 3D animation, spectacular graphics or cater strictly to bonus games. Our site offers software pages for all of the major online slot providers.

Below are the top five online slots software companies that license games to online casinos. Each company page gives a complete overview of the various online slot games each brand offers, in addition to a list of the top five sites each company powers.  You can view the five most popular software developers below or see an overview of all the online slot companies here.

How We Rate Online Slots

Readers might wonder how we arrive at our conclusions. At the start, we collect basic facts about the online slot. Our reviewers discuss jackpots, paylines and the main features each online slot has. After we give an overview, our reviewers describe the coin denominations, jackpots, bonus games and other online slot features in greater detail.

  • Graphics and Sounds
  • Theme
  • Gameplay
  • Developer
  • Reels & Paylines
  • Bonus Features
  • Jackpot
  • Return to Player (RTP)
  • Overall Rating

Graphics and Sounds

With offline and online slots, graphics make games more entertaining and pleasant to play. Sounds enhance the graphics with sound effects, music, and soundbites. With land-based slots, the cabinet’s display also matters.

Some online slots developers like Net Entertainment are known for their cinematic graphics. Microgaming and Playtech don’t have the same graphic quality as NetEnt, but still have graphics that match any other designer. US slot companies like RTG and Rival might not be up to that level, but still offer solid graphics.

Theme

Almost all slot games have a theme like the Old West, Ancient Egypt, or Chinese mythology. Other common themes are Las Vegas gambling, exotic tourist spots, various sports, and both Greek and Norse mythology. Superspies, superheroes, and time periods are common, as well. The possibilities are virtually endless.

Slot themes began with the first slot machine designed by Charles Fey in 1895: Liberty Bell Slots. Mechanical slot machines had simple designs, so fruit symbols, stars, and bars were common reel symbols. Even these 3-reel slots tended to have a theme, though they were rudimentary.

Some online slots take their theme from a pop culture franchise. You’ll see licensed slots based on tv shows, movies, comic book characters, and pop music acts.

Gameplay

Gameplay is important, too. Is the game fun to play? Does it have enough special features to keep things fun? Does it have enough winning spins to make the game interesting? Are the controls easy to use? Are the payouts easy to understand? In online slots, does the software work with your desktop computer or mobile phone? We rate slots according to these criteria.

Reels and Paylines

The reels are how many vertical rows exist on the game screen. Online slots usually have 3 reels or 5 reels, though 6-reel and 7-reel slots exist. Extra reels sometimes appear in bonus games, often as a Big Reel.

Paylines determine the winning combinations on a slot. The many lines trigger, so the number of paylines tells you how many reel combinations wins. Some slots don’t have paylines, but have winning combinations. Examples include “243 ways to win” and “1056 ways to win” slots.

Developers

The slot company that designed the game is important to many players. Gamblers like certain games, so knowing a developer helps them find their favorite slots. Also, companies like IGT, NetEnt, Microgaming, and RTG are known for good graphics, big jackpots, or many features, so knowing the design house helps players find the type of slots they like.

Bonus Features

Bonus features enhance an online slot’s gameplay. In fact, players love features so much they’re often the first thing mentioned in game ads. Examples of bonuses include wild symbols, scatter symbols, free spins, bonus games, and multipliers. Each of these gives the player a benefit beyond the main game, thus drawing them to a title.

Wild symbols complete winning combinations, increasing a player’s odds. Free spins and bonus games give players the change to win cash without risk. Scatter symbols unlock free spins, bonus games, or multipliers. Multipliers increase an online slot jackpot’s prize money anywhere between 2x or 100x the normal prize.

Features have many variations. For instance, you’ll find online slot games with stacked wilds, expanding wilds, sticky wilds, and cascading wilds. Also, these are the basic features. The gamble feature and bonus wheels are also popular.

Jackpot

Nothing draws players to an online slot more than its jackpot. Traditional 3-reel slots have jackpots that are hundreds if not thousands of times the original bet. Once electronic slots became popular and 5 reels were possible, the jackpot increased into the tens of thousands. Eventually, designers created progressive jackpots, where the top prize reached into the hundreds of thousands (or millions) of dollars.

Progressive slots like IGT’s Wheel of Fortune and MegaBucks are among the most popular games in the casino world. Online progressive slots like Mega Moolah are sought by online and mobile players. As a general rule, the higher the jackpot, the lower the return-to-player. This isn’t always the case, but gamblers who play progressive slots should understand the chances of winning are small and they’ll have more losing sessions.

Return to Player

Finally, online slot players seek out games with a high return-to-player (RTP). This is the theoretical amount you can expect to have paid back in prize money. A game with a 97% RTP means you’ll win back $97 of every $100 you wager. Just like blackjack and roulette, players want to know the RTP of a game, so we make that a part of our rating when published.

Guide to Online Slots Features

This section gives a brief description of the key factors that draw players to slots: common slot features, bonus games, and jackpots. Each of our slot reviews focus on these features, while giving a player a quick overview in our “In a Nutshell” section.

Popular Slot Machine Features

Each review gives a snapshot of six popular features that online slots often have. With simple highlighted icons, you can see if the slot being reviewed has these features.

  • Free Spins: Spins that cost nothing and carry no risk.
  • Bonus Round: Interactive bonus games, Mega-Spin Wheels, or free spin rounds.
  • Wild Symbols: Reel icons that substitute for most or all other symbols on the reel.
  • Scatter Symbol: Valuable wherever they appear on reels, these often unlock bonus games.
  • Multipliers: These multiply the value of a prize, ranging from 2x to 100x the payout.
  • Mobile Slot: Whether the slot is compatible with Android or iPhone devices.

Coin Denominations and Jackpots

Coin options tell a player what the minimum or maximum bet on a slot machine is. Is an online slot for penny players, mid-stakes gamblers or high rollers?

Jackpots tell the biggest prize available. Three-reel classics often have fixed jackpots in the low thousands of dollars, which are more attainable. Progressive slots have accumulated jackpots that grow into the hundreds of thousands or millions of dollars.

Bonus Rounds & Fun Bonus Features

Bonus rounds take a break from the main game. They offer players a chance to win big prizes without risking their bankroll.

Fun bonus features include a variety of wild symbols like stacked wilds, expanding wilds and sticky wilds. It also includes interactive bonus games, multipliers, re-spins and the Gamble Feature.

Review Feature: An Online Slot in a Nutshell

Toward the end of each slot review, we provide a short summary of the online slot. This summary provides key features, jackpot information and the developer. This gives players a quick review of the game to remind them of its pros and cons.

Mobile Slots Casinos

Most online slot games are now available for mobile play. Our mobile slots guide outlines where you can play for free as well as for real money. We focus mainly on Android slots and iOS slots for iPhone and iPad, but also discuss the BlackBerry and Windows Phone operating systems.

In each review, read through our mobile section, which includes comparison reviews, a dedicated page for each device, and more. This includes which casinos offer a mobile app for your device – which is most online casinos in 2021. Like online slots, you can play mobile slot games for real money or free.

How to Play Slots

Now that you’ve chosen an online slot to play, you’ll want to know how to get started. If you’re never played online slots, here’s a step-by-step guide to playing slots online.

  1. Join an Online Casino: Register for a player account, then make a deposit using your favorite payment method. Accept the welcome bonus and play slots to clear the requirement.
  2. Pick a Slots Game: Next, click on “Slots” at the games menu at the top of the screen. Choose the online slot with the theme or features that stands out to you.
  3. Choose Paylines: Pick max paylines to activate the biggest jackpot. Most online slots require the max lines for the max prize.
  4. Make a Slots Bet: Once the online slots screen appears, find the bet options at the bottom of the screen. Click plus (+) or minus (-) to increase or decrease the bet. Choose a comfortable bet level.
  5. Hit Spin: Keep in mind the overall bet is the coin denomination times paylines. Once you have the right bet level, hit spin for gameplay.
  6. Cash Out Winnings: Continue the same process until you time of the slots session or your bankroll is gone. If you hit the jackpot or have big winnings, cash out your prize money.

Online Slot Tips

Now that you know slot machine outcomes are based on a random chance, you can choose your favorite online slots with confidence. New online slots players should avoid any pitfalls by following the tips below. Remember if you don’t enjoy a game, casino sites offer 100 or more online slots, so you should move on to the next one.

5 Reel Slots

Higher Denominations Equal Better RTP

Return-to-player (RTP) is a percentage you can expect to win back. The higher the RTP, the more you’ll win over a long period of time. If you play at higher coin denominations, the RTP is higher on most slot machines.

As a general rule, the higher the coin denomination, the higher the return to player. This is more a tip for Las Vegas slots, but it also applies to online slots.

Return-to-player (RTP) is a percentage you can expect to win back. The higher the RTP, the more you’ll win over a long period of time. If you play at higher coin denominations, the RTP is higher on most slot machines.

As a general rule, the higher the coin denomination, the higher the return to player. This is more a tip for Las Vegas slots, but it also applies to online slots.

Welcome Bonus

Bet Max Paylines to Activate the Main Jackpot

Often, a player must make the max bet (max paylines) for an online slot’s biggest jackpot to be active. Read the rules to make sure.

Especially if you play progressive slots, make certain you wager enough to trigger the progressive jackpot. Most progressive slots require the max payline to be active. If you hit a royal flush on a progressive jackpot, you want the progressive to be active.

Often, a player must make the max bet (max paylines) for an online slot’s biggest jackpot to be active. Read the rules to make sure.

Especially if you play progressive slots, make certain you wager enough to trigger the progressive jackpot. Most progressive slots require the max payline to be active. If you hit a royal flush on a progressive jackpot, you want the progressive to be active.

Cashback

Play Within Your Budget

Have a bankroll of discretionary cash you can spend without difficulty. Play for fun and don’t expect to win big jackpots. Online slots are entertainment, so treat them like you would tickets to a sporting event or concert. Or if you don’t have a big budget, treat them as you would a trip to the movie theater or restaurant. If you win playing the slots, even better.

Have a bankroll of discretionary cash you can spend without difficulty. Play for fun and don’t expect to win big jackpots. Online slots are entertainment, so treat them like you would tickets to a sporting event or concert. Or if you don’t have a big budget, treat them as you would a trip to the movie theater or restaurant. If you win playing the slots, even better.

Risk Free Bets

Choose Flat-Top or Progressive Slots

In online slots, a fixed or flat-top jackpot usually has better odds than progressive jackpots. If not, winning combinations hit more often than on progressives slots. On the other hand, progressive slots have lottery-style jackpots. Based on your preferences and ambitions, choose a smaller fixed jackpot slot or a progressive slot.

In online slots, a fixed or flat-top jackpot usually has better odds than progressive jackpots. If not, winning combinations hit more often than on progressives slots. On the other hand, progressive slots have lottery-style jackpots. Based on your preferences and ambitions, choose a smaller fixed jackpot slot or a progressive slot.

Fun Themes

Choose Fun Themes

If you plan on long online slots sessions, pick interesting themes with graphics and sounds you like. You want the game to be entertaining.

If you plan on long online slots sessions, pick interesting themes with graphics and sounds you like. You want the game to be entertaining.

Video Poker

Research Online Slots

Read our online slot reviews to find the games with the jackpot types, RTP, and features you like. Pick your game based on the tips below.

Read our online slot reviews to find the games with the jackpot types, RTP, and features you like. Pick your game based on the tips below.