How do slot machines work?

Is a casino even a casino without slot machines? If there is one game that has made the international casino world the bright temples to potential wealth and excitement it is, it must be the slot machine. The bright lights, the spinning reels, the bells, whistles, sirens, and sounds of coins dropping into the tray – they are the ultimate symbol of the casino world and have changed gambling since their introduction in the late 1800s.

But how do they actually work? went deep into the inner working of slot machines, past and present, to give you an exclusive insight into how these popular machines work.

How do slots work?

It’s super simple. You pull the handle or push the button. The reels spin. The reels stop. You win or lose.

Simple yes but also … no. On the surface they seem obvious: some symbols on moving wheels and a mechanism to make them spin and stop. But how they do what they do and why they do what they do is part of the mystery behind slots.

First, let’s get some terms out of the way:


Reels are the drums with symbols on that you can see spinning and stopping through the window or on the screen. In old slot machines they were physical drums with the symbols printed onto them. Modern video slots and online slots use graphics and software to simulate the action and appearance of reels.

Reels usually run from top to bottom of the slot. When you see a slot description like 3×5 it means it’s a 3-reel slot with 5 rows (the rows run from left to right). Think of it as a grid with 3 columns and 5 rows to give you a total of 15 symbols that you can see (there are a lot more symbols that you can’t see and so don’t affect your game).

Modern video slots often change up their format to offer 3, 5, 7, or even more reels, and can bring players all sorts of variations on the rows like a 2, 3, 5, 3, 2 configuration (a diamond shape rather than a square-ish grid).

how do slot machines work?

Coin slot

This is what slot machines are named after – the slot that you put your coin in to start the game. A lot of modern slots, and online slots especially, have done away with the need for coins and you play completely digitally with your bankroll ‘deposited’ directly into the machine. Physical slot machines in land-based casino often operate using a card that is preloaded with your bankroll and is inserted directly into the machine.

Technically, that still makes them ‘slot’ machines as they still need a slot that you insert your coins, your paper money bills, or your card into.

How do slot machines work?


Also called a handle, this is the old-timey mechanism for starting the reels spinning. You pulled down on the handle and a spring inside the machine started the reels spinning.

It’s also the origin of the name ‘one-armed bandit’.

Modern land-based and online casinos have largely done away with the lever and operate using a ‘spin’ button.

how do slot machines work?

Play buttons

These are the buttons that have replaced the lever. Most slots have a selection of different buttons including bet, select bet, max bet, and turbo.

how do slot machines work?