The Evolution of Online Slots in 5 Games

How Have Online Slots Evolved Over The Years? 

There's no denying that slot machines have changed a lot in the last 20 years. 

Once upon a time, you could score three cherry symbols on a line and the job was a good'un; you'd bag enough change to pay for your next pint.

Now, though? Online slots are a whole different kettle of fish, with different paylines, symbols, and bonus features to worry about. 

While hundreds of games could tell this story, we've picked out five games that have really shaped how players experience online slots.

The Birth of the “Book” Era (Book of Ra – 2005)

Now, a list of revolutionary slots wouldn't be complete without a mention of Novomatic's 2005 slot, Book of Ra, paving the way for thousands of Ancient Egyptian slots to follow. 

But that's not all. This was the OG “Book” game, spawning an entire genre that's still dominating casinos to this day.

The idea was simple but worked like a charm: collect three of more Book of Ra symbols to unlock free spins. 

This release took players on a whirlwind exploration adventure, where the possibility of striking gold was always just a spin away. 

Book of Ra may be basic at its core, but it’s become a cult classic for a reason.

Simple Yet Effective (Starburst – 2012)

It's no surprise that Starburst makes an appearance on this list.

You may recognise it, as it's often plastered all over the front of slots sites as part of their welcome bonus, usually with free spins attached. 

The entire theme plays into retro-style graphics of the 90s, with the sights and sounds of bygone arcades brought back to life (NetEnt's own words).

There's a heavy hit of nostalgia, mixed with space symbols and dazzling diamonds.

NetEnt knew exactly what they were doing with this 2012 release. Slot players are like Gollum — we see something shiny and sparkly, and we immediately want in. 

Now, Starburst isn't anything groundbreaking with complex mechanics or rules.

It's all about being ridiculously easy (to the point where anyone could pick it up and play), with expanding wilds and the Win Both Ways technology pretty much carrying all the weight. 

Despite being over 10 years old, Starburst still holds its weight with its mobile compatibility that make it a dream to play on smartphones. 

Starburst Base Game

Megaways Hitting the Big Time (Bonanza – 2016)

Bonanza didn’t just change the game — it practically bulldozed the old one. 

Up until this point, most slots were about fixed paylines: horizontally and diagonally from left-to-right. A bit basic, but still fun. 

Then along came Big Time Gaming in 2016 with the Megaways mechanic, blowing fixed paylines out of the water. 

With dynamically-changing reels, Megaways slots like Bonanza can offer up to 117, 649 ways to win that make each spin as unpredictable as the last. 

While Bonanza wasn't the first slot to use this mechanic (that honour belongs to Dragon Born), it was the one that blew up, so to speak, with its goldrush theme and HD graphics. 

And let's be honest: without Bonanza, half of the modern slots scene wouldn't even exist without cramming that iconic Megaways feature in there. 

Middle Finger to Convention (San Quentin – 2021)

When Nolimit City dropped San Quentin in 2021, they didn’t just push boundaries; they torched them and danced on the ashes. 

This is a studio that's built their reputation from the ground-up on tongue-in-cheek, middle-finger humour, and nowhere is clearer than here. 

The whole thing oozes “don’t drop the soap” jokes, barbed wire edge, and the kind of dark wit that makes you grin and grimace at the same time.

The gritty graphics show just what NLC are capable of: tatted inmates, handcuffs, and grubby basketball courts that make you feel like you need a tetanus shot after playing (or escaping). 

Gameplay-wise, San Quentin is a madhouse with a shedload of innovative mechanics like xWays, splitting symbols, Enhancer Cells, jumping wilds, Lockdown spins, and more.

It’s volatile, it’s unforgiving, it's funny, and it became a cult hit, even spawning a sequel with San Quentin 2: Death Row in 2025. 

We can safely say that NLC are like the Marmite of the slots world: love 'em or hate 'em, you can’t ignore the impact they've had.

Big Loss…

Slot Features on Steroids (Pirots 4 – 2025)

Moving away from controversial slot themes, ELK Studios hatched the iconic Pirots series in 2023, combining parrots with pirates in the form of the feathered Fearsome Foursome.

Fast forward to 2025 with Pirots 4, the latest instalment in the series that takes the birds to a galaxy far far away, with twinkling stars and even a random floating bowling ball for good measure (don't ask). 

Now, this slot has literally every single slot mechanic and feature under the sun.

Birds of a feather flock together as CollectR returns with a bang. 

In a Pacman-seque mechanic, four birds fly around the grid collecting matching coloured gems and feature symbols, unleashing chaos once the collection meter is completely filled.

Here, ELK have crammed in upgrade systems, wild corner explosions, alien invasions, black holes to reshuffle the entire board, and even a Spacecorn that lets the CollectR birds leap across gaps like Frogger. 

Deep breath, that's not even all.

On top of all of that, you've still got  switcheroos, super bonuses, X-iter bonus buys, and a whole coin-collecting mini-game inside the slot. 

While some may say Pirots 4 is overkill, we'd argue the opposite, having rated it an above-average score of 8.3 out of 10 as it shows just what slot machines are now capable of.

Pirots 4 Super Bonus Game Play

Final Thoughts

Just like Pokemon, slots have evolved from humble beginnings into the behemoths of the entertainment world they are today. 

What started as simple fruit machines with fixed paylines has turned into feature-packed spectacles to keep players second-guessing every spin. 

And thanks to online casinos and mobile play, you don't even need to leave the house!

You can fire up a slot in seconds, whether you're having a cheeky go on the loo or doom-spinning under the duvet at 2am. 

From Book of Ra's ol' reliable expanding symbols to Pirots 4 literally throwing every feature under the sun at you, this journey shows just how much slots have reinvented themselves over the years.

The evolution of slots is clearly far from over.

Who knows what madness is around the corner, but we know we're always here for it.