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What Are Online Slots and How Do They Work?

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Lina Almans

08 May 2023

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Online slots — aka slot games, casino slots, or video slots — are games where players spin 3+ reels displaying rotating symbols. 

Note: Every slot has its own unique stake sizes, paylines (and often different names for them), payout rules, and bonus mechanics.

How Online Slots Work?

Each slot is backed by a Random Number Generator (RNG), a system that uses complex math algos to generate random combinations every time a player spins the ‘reels’ (vertically arranged columns with a set of symbols).

So, when a gambler starts playing (click spin button), the RNG instantly selects a combination of symbols for the reels, which then appear on-screen. The outcome is completely random, meaning each spin is independent of the last, and previous results have no impact on future outcomes.

casino slots example

Look, we have three strawberries diagonally! We won something, we need to look at the paytable.

If symbols line up in particular patterns or positions (called paylines), this forms a winning combo, leading to prizes or unlocking bonus rounds in accordance with the game’s ‘paytable’, which shows:

  • All the possible winning combos
  • What each symbol is worth
  • And the bonuses (if available)

The winning combination is described in the rules of each slot. Often the player must catch the lines, as here.

Sometimes lines are not needed. Here winning combination are paid for symbols appearing in any position on consecutive columns from left to right (called WAYS PAYS).

1xbet

Alongside RNG, another vital metric for slots is Return to Player (RTP), which estimates the long-term % of all bets that will be returned to bettors. Most online slots have an RTP ranging from 93% to 97%, meaning a game with a 96.3% RTP will theoretically return $96.3 for every $100 wagered.

Note: Malfunction voids all pays and plays.

How to Access Paytable?

If you’re wondering where to find paytable, look for the “i” or “?” (usually on/near the game screen). Some games place this info under a menu or grid-like symbol.

Paylines and Stake Size

The number of winning combinations — typically 5 to 25 on most slots (though it can be even more) — directly impacts your chances of landing a win.

But here’s the deal: more winlines = better odds, but each line you activate increases your total stake. For example, in a 5-payline Ultra Fresh slot, you could choose to bet on just 3 lines to keep your costs down. However, this limits your chances of hitting those less obvious patterns like zigzags, leaving you with horizontals.

1 line

Usually, each reel holds about 10 symbols, and slots typically have between 3 and 6 reels, meaning that this setup can lead to thousands of winning combos.

What is Slot Volatility⚡ ?

Slot volatility is a measure of the game’s risk and payout behavior. It determines two key things: how often you win (frequency) and how much you win (size of payouts).

Here’s a quick breakdown of volatility levels:

  1. Low: Wins come almost every spin, but most payouts barely cover your stake.
  2. Medium: A sweet spot — decent-sized wins pop up at a fair pace.
  3. High: Rare payouts, but when they hit, they hit hard.

The metric is either displayed when the game loads or found by clicking “i” or “?” icon. Sometimes, it’s marked with symbols like lightning bolts ⚡(e.g., 5 bolts = high).

Sweet Bonanza at 1Win with Medium volatility (3,5 bolts)

Types of Online Slots

According to gambling software provider EGT Digital, here are some of the most common ones depending on the reel and payline configurations:

The Most Popular Online Slot Games

According to The European Gaming top 15 of most popular online slots in 2024, here are some of the year’s most-played slots:

  • Gonzo’s Quest Megaways (provider: Red Tiger Gaming w/ NetEnt)
  • Dead or Alive 2 (provider: NetEnt)
  • Sweet Bonanza (provider: Pragmatic Play)
  • 3 Hot Chillies (provider: 3 Oaks Gaming)
  • Book of Dead (provider: Play’n GO)
  • Le Bandit (provider: Hacksaw Gaming)

Best Online Slot Software Providers

  • Amatic
  • Play’n GO
  • BGaming
  • Evolution
  • Pragmatic Play

What Are Multiplayer Slots (Community Video Slots)?

Multiplayer slots allow multiple players to spin simultaneously, each influencing the outcome for others in a community-style game format. These community video slots can accommodate up to 6 players.

FAQ

What is RNG in online slots?

RNG, or Random Number Generator, is a system that ensures every spin on a slot machine is completely random and independent.

What is Return to Player (RTP)?

RTP is the percentage of your bet that a slot game is expected to pay back over time. Typically, RTP is around 95-96%, meaning you’ll see that amount returned on average in the long run.

What is the biggest online slots win of all time?

The largest online slots jackpot ever was €38.5 million in December 2023, won through the WowPot! progressive jackpot on Wheel of Wishes, a slot game developed by Games Global’s Alchemy Gaming studio.