The slot machine has been through more changes than almost any other casino game. What started as a coin-operated mechanical device in a San Francisco workshop is now a digital format played on phones and computers anywhere you have internet access.
The core idea, however, hasn’t changed much at all.
Charles Fey, a mechanic based in San Francisco, built the first recognisable slot machine in the 1890s. His design, known as the Liberty Bell, had three reels printed with five symbols: horseshoes, diamonds, spades, Hearts, and a cracked bell. You inserted a coin, pulled a lever, and waited for the reels to stop. It was entirely a game of chance. Those early machines became known as one armed bandits, a nod to the lever on the side and the way they could steadily drain a player’s coins.
How Fruit Symbols Ended Up on the Reels
As restrictions tightened in parts of the United States in the early 1900s, casino operators looked for ways to keep the machines in use. One approach was to replace the traditional symbols with fruit imagery and award prizes like sweets and chewing gum rather than coins. The logo of the Bell Fruit Gum Company became the bar symbol that still appears on slot games today. Fruit machines, as they became known in the UK, arrived in British pubs during the 1960s and quickly became a familiar part of that setting.
The Move to Digital
Electronic components started replacing mechanical parts in machines from the 1960s onwards. By the 1980s, video screens had started replacing physical reels. The most significant shift, though, came with the introduction of the Random Number Generator (RNG). This software produces a new random outcome for every spin, meaning each result is entirely independent of the one before it. There is no pattern, no predictable sequence, and no way to influence what comes next.
When online Slots arrived, the RNG moved from a physical machine to software running on a server. The reels you see on screen are a visual representation of that process. Nothing mechanical is happening. The result is determined the moment you start a spin.
How Online Slots Work Today
Modern online Slots vary considerably in how they’re built. Some use fixed paylines, where matching symbols need to land in set positions. Others use different mechanics, which could change the number of symbols on each reel with every spin, producing a different number of possible combinations each time, or have winning combinations come from groups of matching symbols rather than lines.
UK regulations set the maximum stake at £5 per spin for players aged 25 and over, and £2 per spin for those aged 18 to 24. Every UKGC-licensed online slot must display its Return to Player (RTP) percentage and volatility rating.
What’s Stayed the Same
Despite all of it, the basic mechanic has held. You place a credit, the reels spin, and the result comes down to chance. The lever is gone. The fruit symbols are mostly optional. But the principle Fey built into his Liberty Bell machine in the 1890s is still the foundation of every online slot available today.
