A timeline of slot mechanics & trends

Gambling has been ubiquitous among humans for thousands of years at least, and has even been observed among birds and monkeys. In this article, we will not explore all of its known history, but rather focus on one modern, incredibly successful branch of its evolution - the slot machine.

Before we look at recent trends in slots, it is worth going back to the beginning where it all started - the second industrial revolution.

The first widely known innovation is the 1891 Sittman & Pitt poker-machine where players could drop a coin and get a randomly generated poker hand. This machine lacked automatic payouts however and it only featured mechanics from Poker.
This is why the first actual slot machine is regarded to be the 1895 Liberty Bell by Charles Fey. This device had automatic coin payouts and it featured a 3x1 grid with one winning line, with the symbols being playing card suits - the same mechanics that are still alive and kicking today, but in a minimal variant.
Interestingly, Charles only made this machine as entertainment for his clients while they were waiting for their cars to be serviced in his auto mechanic shop. Little did he know its popularity would rise so much amongst his customers that he would soon be inclined to make these machines full time.

By around 1910 there was serious competition in the space and gambling laws were being put into place in the US - that is when the “Fruit slots” emerged - machines which paid out in fruit flavored gum instead of real money, hence why they often had fruit symbols instead of cards or something else.

At this point we start to see how the modern look of slots came to be, but there were still a lot of innovations to be made. 

In 1976, Fortune Coin came up with the video slot - a machine where all the gameplay is powered by electronics rather than a mechanical setup. It used a modified Sony television as the screen. This revolution meant that slots would only be limited by hardware and software now, leading to countless new possibilities. And they did appear:

In 1986, IGT came up with the shared progressive jackpot, a mechanic still very popular today, both in online and land based machines.

By the 1990s, the industry had most of what we recognize today - multiple paylines, scatters, wilds, free spins. Arguably one of the most notable games of that era is the 1996 IGT Wheel of Fortune - a game where waiting for the bonus is the most important part of the game loop, rather than simply striving for a line win. This mindset essentially persists today, though with the small twist of being able to buy the bonus directly.

In the next 10 years, video slots continue to get more sophisticated, culminating in more well-known innovations.

In 2005 Book of Ra is released and gradually becomes a massive success with its “One symbol becomes special and expands during the free spins” formula. This formula is still being used today by countless studios, and “Book of” games are quite easy to come across. At around the same time though, in 2006 Mega Moolah is released by Microgaming, who were very dominant at the time. The main feature of this game is the insane progressive jackpot wins, creating world records for largest online slot wins at the time, where a player won over €6M in 2007, just a year after release.

Slowly but surely the modern landscape is being shaped, but it doesn’t stop there:

In 2010 Netent comes out with Gonzo’s quest and popularises the toppling reels - a very important mechanic, as it makes your spins last longer and makes for a much more dynamic and interesting gameplay experience. The effects of this are seen today where many games have a ton of “interaction” happening in order to reach the final win.

Sure enough this would pave the way for much more variety - ways pay become very popular at around this time, with Big Time Gaming coming out with Megaways around 2016, popularising it with their timeless Bonanza Megaways. This feature allows each reel to have variable size, making for countless different grids rather than a static 3x5, for instance. It is also quite a high volatility game for 2016 standards, which would soon become part of a bigger trend.

In 2017, Reactoonz comes out, arguably being the one to popularise cluster pays. Hold and win games start to become mainstream as well, and the stage is now set for the immensely influential Covid era, starting in 2019:

As Pragmatic Play make their push with high volatility, multiplier based releases like Sweet Bonanza and as Bonus Buys become popular, the world gets shut down for a few years, driving greater engagement with online slots and gambling streamers. The growing influence of high wins shown on social media and the ability to play all the time inevitably leads to very high volatility online slots becoming a huge part of the ecosystem, and forces studios to compete - this is where we frequently start seeing base game wins north of 10,000x your bet and increasingly convoluted game rules combining 5-10 features, neither of which was mandatory some years back.

As Covid ended, things have not changed too much - in 2026, online slots are as complex as ever, combining tons of features and promising very high returns, even without jackpots. In the meantime, some markets are still dominated by Hold-n-win games which focus not necessarily on high returns but on an increasing amount of interactivity and visual spectacle.

What does the future hold? In my opinion, there will be a correction when it comes to the popularity of very high volatility slots, with some players and studios coming back to more well rounded games, especially after the exhaustion of dead or almost-dead spins on a 40,000x max win game. Will this happen, only time will tell!