Last updated: 12 November 2025
The evolution of slots
Slot machines have come a long way since their humble beginnings in the late 19th century. The very first slot, the Liberty Bell, was invented by Charles Fey in 1894. It featured three spinning reels and a simple payout system based on matching symbols. That mechanical marvel became the blueprint for the decades of slot innovation that followed.
When online casinos began to appear, developers quickly recognised the potential of bringing slot games to the digital space.
Today, online slots are one of the most popular forms of casino entertainment in the world. They blend art, maths, and technology into one endlessly varied experience that caters to all types of players.
Types of online slots
Modern online casinos offer a diverse range of slots, each with its own style and mechanics. Understanding these categories can help you find the kind of gameplay you enjoy most.
- Classic Slots: These are inspired by the original fruit machines. They feature simple layouts with three reels, minimal paylines, and familiar symbols like cherries, bars, and sevens. They’re perfect for players who prefer a traditional, straightforward, nostalgic experience.
- Video Slots: The most common type of online slot today. Typically, video slots have five reels and are reasonably simple, mechanically speaking. However, their impressive visuals, immersive themes, and entertaining bonus features make these slots stand out.
- Progressive Jackpot Slots: These games are linked across networks, meaning every player contributes to an ever-increasing prize pool. This means jackpot values on popular progressive slots can reach absurd heights, promising a life-changing prize to the lucky winner.
- Megaways Slots: Introduced by Big Time Gaming, Megaways slots feature a dynamic reel structure with thousands of possible paylines on every spin. They’re unpredictable and exciting, ideal for players who love variety.
Slot mechanics explained
Slots may look simple, but under the bonnet lies a complex mathematical system that determines how they work. Here are the key slot concepts every player should know:
- RTP (Return to Player): This is a percentage that indicates how much a slot is expected to pay back to players over time. For instance, a 96% RTP means that, on average, the game returns £96 for every £100 wagered. It’s not a guarantee of individual results, but it provides an accurate guess based on long-term averages.
- Volatility (Variance): This describes how often and how much a slot pays out. Low-volatility online slots provide frequent but smaller wins, while high-volatility games pay far less frequently, but much larger sums when they do.
- Symbols and Features: Common slot symbols include wilds (which substitute for other symbols), scatters (which trigger bonuses), and multipliers. Online slots often add creative twists, such as cascading reels, expanding wilds, or sticky symbols that stay in place for multiple spins.
Understanding these mechanics can help you choose games that match your preferred level of excitement and risk.
Who develops online slot games?
With slot games being the most popular form of casino gambling, there are plenty of developers making them. Here are a few of our favourite slot gaming heavy hitters:
- NetEnt: Known for visually stunning slots, NetEnt focuses on sleek animations and accessible gameplay.
- Pragmatic Play: Famous for high-volatility titles with strong mobile compatibility.
- Play’n GO: This developer is known for adventure-themed slots and well-balanced gameplay.
- Microgaming: A pioneer in online casino software, responsible for Mega Moolah, one of the most iconic progressive jackpot slots ever made.
- Big Time Gaming (BTG): Innovators behind the Megaways mechanic, reshaping how players experience paylines and potential wins.
- Relax Gaming, Yggdrasil, and Push Gaming: Modern developers pushing boundaries with creative features and storytelling-driven designs.
These developers continuously compete to create fresh, entertaining experiences that combine fair gameplay with exciting rewards.
Final thoughts
Online slots are constantly evolving yet remain rooted in over a century of gambling history. From simple three-reel machines to multi-feature video slots, they offer an exhilarating experience for everyone.
Whether you’re spinning for nostalgia, excitement, or relaxation, the world of slots always has something new to discover.