No Tricks, Just Clicks: How Do Online Slot Machines Work?

Spin me right round: Slot machine basics

Be it an online slot on your phone screen or a slot machine cabinet on the casino floor, slots are considered a ‘soft’ casino game.

Translation: you need very little skill or previous knowledge to jump into the action, unlike table games, that usually require you to know more rules. Table games also allow you to practice and strategize your gameplay in a way that can affect the outcome.

When playing slots, you just need to set your betting amount and spin the reels that have various pay symbols on them. If you land a winning combination of symbols on a payline, you will win a prize according to your stake and the value of the pay symbols. But these are the bare bones.

From classic, 3-reel fruit machines with one payline to Megaways slots with 117,649 ways to win at every single spin, there are thousands of online slots — each being unique. Still, there are some common fundamentals.

Randomly yours: How RNG runs the show

Why would you bet your money on an online slot that could be rigged and programmed to make you lose money? Or why would the online casino let you play on a slot that would pay out on every spin and make it go bust?

As online slots are games of chance, the outcome of every single spin must be totally random and independent. For this reason, every online slot has a Random Number Generator (RNG), which is a built-in algorithm that ensures the random outcome of every spin.

So, the myth of a slot being ‘hot’ and ready to pour out winnings and make you rich any second now, as it hasn’t done so in a while, or ‘cold’ because it just handed a win, is just a superstition. The RNG will ensure that every spin is up to chance, so think of it as a mythbuster. 

Covers Expert Analysis

"Most reputable online slot providers will have their games certified by third-party testing companies that audit the RNG regularly. These agencies include GLI, TST, and eCOGRA. You can find the certification on the casino’s website (usually in the footer)."

Ziv Chen, Covers News Editor

How much do slots really pay? RTP has the answer!

Now that we’ve established that every spin is random, let’s move on to something that’s set in stone. If there’s something an online casino won’t leave to chance, it’s the profits (or losses) it will make from its online slots.

Every online slot has an RTP (Return to Player), which is defined as the percentage of the total wagers paid out to players in winnings. For example, a game with an RTP of 96% (the industry average for online slots) will pay back in winnings $0.96 for every $1 wagered.

However, it is essential to understand that the RTP is a statistical average calculated over billions of spins. So, while one lucky player can enjoy a huge winning streak, another can be down on their luck and lose their entire bankroll. 

While the average RTP of online slots is around 96%, you will find games that offer an even higher return. Here are a few examples:  

• Mega Joker — RTP up to 99%
• Blood Suckers — RTP 98%
• Rainbow Riches Pick N Mix — RTP 98%
• Starmania — RTP 97.87%
• White Rabbit Megaways — RTP 97.77%

Some online slots may have variable RTPs, which will depend on the stakes and prizes you are playing for. Most slots will display the RTP in the game’s information tab.

Risk it for the biscuit: Understanding slot machine volatility

From "Go big or go home" to "No guts, no glory" and every cliché in between — online slots offer higher potential rewards to those willing to risk more in their quest for riches.

This risk-reward ratio is marked in online slots by the game’s volatility, which defines the frequency of winning spins a slot will produce. If you play on a high-volatility slot, you won’t trigger wins often, but you are likely to land more winning spins if you play on slots with low volatility.

Naturally, medium volatility online slots are somewhere in between. 

So that covers the risks — but what about the rewards? This is where the winning amounts come into play. Although you will most likely wait longer between winning spins when playing on a highly volatile slot, once you do trigger a win, it will probably be bigger than the smaller, albeit frequent, wins you can expect from an online slot with low volatility.

Here’s a cheat sheet to help you choose the volatility that’s right for you:

Online vs physical slots: What are the differences?

While spinning the reels on your phone and on the casino floor have many similarities, the experience is quite different.

While both physical and online slot machines operate on the same basic principles — randomized outcomes and symbol-based gameplay — the player experience differs dramatically between the two formats.

Physical slots offer a social, sensory-rich environment that appeals to players who enjoy the ambiance of a casino: buzzing crowds, celebratory lights, and on-site comps like drinks or hotel perks. However, they come with notable limitations: lower Return to Player (RTP) percentages, fixed slot selections, and jackpots confined to a single casino or region. 

Online slots, on the other hand, offer unparalleled flexibility and broader value. Players can spin anytime, anywhere, often taking advantage of free online slots in demo mode before wagering real money. With higher RTPs, global prize pools, and a wider variety of games — including modern themes and bonus features — online slots cater to a more individual, convenience-driven player.

The trade-off is a more isolated experience, with digital perks (like in-game bonuses) replacing the physical comps and shared excitement of a casino floor.

Behind the spin: Understanding the forces that shape your game

Now that you’re familiar with each individual force, it’s time to combine them into the Holy Trinity of online slots — starting with the most important point: While RTP, RNG, and Volatility all combine to make the slot, each force is still independent of the other to an extent.

• Whether high, medium, or low volatility, the outcome of every spin is always random.
• The outcome of every spin is random regardless of the slot’s RTP.
• Slots with high or low volatility can have either high or low RTPs.
• RTPs are calculated over billions of game sessions and can never predict a single player’s win.

The most important thing to understand while playing online slots, similar to any other type of casino game, is that winning is always up to chance, and gambling should always be seen as entertainment and never as a certain way to make money. So have fun, and always gamble responsibly.