How can online slot machines differ from one another?
From a distance, online slots seem fairly simple – spin the reels and match the symbols on the screen to win. But beneath the surface, there is a complex web of mechanics, algorithms and design choices that make each one of these machines unique.
Each element, from reels and paylines to volatility and bonus rounds, changes the experience fundamentally, with some slots being slow burning and strategic, rewarding patience, while others are high-stakes, offering rapid payouts but at a much higher risk.
Reels and rows – the building blocks
● 3 reel slots – These are the simplest form of slot machines you can find in modern times and are often referred to as classic slots. They are the direct descendants of old mechanical slot machines, offering a limited number of paylines and straightforward gameplay.
● 5 reel slots – These are the standard version of modern slots, carrying a simple 3x5 grid and offering additional symbols, combinations and space for complex features.
● Unlimited reel slots – Found in some advanced slots, especially those powered by the Megaways mechanic, where the number of symbols on each reel can vary on every spin.
Paylines vs ways to win
● Fixed paylines – You must land a matching symbol in a predefined order – left to right, starting from the first reel. The more paylines a game has, the more opportunities you'll have to form a winning combination.
● 243 ways to win – Such slots use ways to form winning combinations instead of paylines. The wins are formed by matching symbols falling on adjacent reels. This is a much more dynamic structure and offers a more immersive experience.
● Megaways – These games change the number of symbols on each reel with each spin, leading to tens of thousands of ways to win on a single spin.
Why does any of this matter? Because each one of these aspects can completely distinguish one slot from another. A fixed payline slot forces you to spin the reels until a combination falls on a fixed path, while a ways-to-win slot offers you a chance to get paid for a cluster of matching symbols, no matter where it is on the grid.
RTP and volatility – the true risk behind every spin
After the inner mechanics, the next biggest thing that can separate one slot from another is its maths. In slot mathematics, there are two main quantitative parameters: RTP and volatility.
Return to Player (RTP)
RTP is the long-term expected payout of a slot machine. It's calculated as a percentage.
For instance, an RTP of 95% means that for every £100 wagered on a slot, it will return £95 back to the players. So the house edge is 5%.
Types of slots based on RTP are:
● High RTP – 97% and above. Better long-term returns.
● Standard RTP – 95-96.9%. Balancing fair wins with casino profitability.
● Low RTP – below 95%. Volatile, can drain bankrolls faster unless they have compensating high-reward features.
The issue with RTP is that it isn't really bound by time or money invested. For instance, it might fulfil its RTP after 2,000 spins or 200,000 spins. So, we can't really take it as a solid parameter. That's where volatility comes in.
Volatility or variance
Volatility defines how frequently and how much a slot pays out.
● Low volatility slots – Small, frequent wins. Best for casual players who want to stretch their bankroll. Examples – Starburst, Aloha! Cluster Pays.
● Medium volatility slots – A balance between small and large wins, offering varied gameplay. Examples – Book of Dead, Immortal Romance.
● High volatility slots – Long dry spells but massive payout potential. Requires patience and a big bankroll. Examples – Dead or Alive 2, Bonanza.
A common mistake players make is confusing RTP with volatility. A slot with high RTP but high volatility can still drain your balance quickly due to infrequent wins.
The heart of the game – special features and bonus mechanics
Modern slots are no longer just about lining up symbols. They’re interactive, with features that add layers of strategy and excitement.
Free spins – the most sought-after feature
Triggered by landing scatter symbols, free spin rounds often come with:
● Multipliers that increase exponentially with each spin.
● Retriggers, where more scatter symbols extend the bonus round.
● Special expanding symbols, like in Book of Dead, where one symbol grows to cover entire reels.
Cascading reels and avalanche mechanics
Instead of traditional spins, winning symbols explode and are replaced by new ones. This means a single spin can lead to multiple wins in succession – a game-changer for high-volatility slots.
Bonus buy feature
Some slots let players pay directly for bonus rounds instead of waiting to trigger them naturally. The price is steep (50x to 200x your bet), but for high rollers, it’s a way to cut out the grind.
Free vs paid slots
Free slots, such as those offered on https://www.johnslots.com/en/slots/free/, let players enjoy games without risking money – perfect for practice and fun. This also allows you to understand the different games better, so if you decide to spend some money, you know which slots are best suited to you.
Paid slots, however, require real wagers but offer the chance to win actual cash.
While free slots provide risk-free entertainment, paid slots bring real excitement with potential payouts, bonuses and progressive jackpots.
Final thoughts – why it all matters
Next time you launch a slot, don’t just spin aimlessly – look under the hood. What’s the RTP? What’s the volatility? What bonus mechanics are in play? Knowing these things won’t guarantee wins but will certainly give you a better gaming experience.