How Online Pokies Work: RNG, Reels and Payouts
Every online pokie is a piece of software with three parts: a random number generator (RNG) that picks the result, a maths model (reel strips, paytable and feature rules) that turns that result into symbols and prizes, and an animation layer that shows it to you. The spinning reels are a display. The result is decided in milliseconds, before the reels stop.
This page explains each part, shows how a payout is calculated, and lists what you can and cannot control. For the wider guide to game types and features, see the online pokies guide.
Step 1: The RNG Picks the Result
When you press spin, the game server requests a random number from its RNG. Modern games use a pseudo-random algorithm that produces numbers with no usable pattern and is cycled continuously, whether anyone is playing or not. Each number is mapped to a stop position on every reel.
Three rules follow from this design:
- Each spin is independent. The RNG has no memory, so the previous 100 spins have no effect on the next one.
- Timing and button technique do nothing. Pressing spin faster, slower or using quick stop does not change the odds.
- The result exists before the animation. Near misses, slow reels and “teasing” scatters are presentation, not information about what is coming.
The Queensland Office of Liquor and Gaming Regulation states the same principles for land-based machines: outcomes are random, independent of previous plays, and the machine is designed to be tamper-proof (Business Queensland: how gaming machines work). For a deeper look at the algorithms and how labs test them, read our RNG explainer.
Step 2: Reel Strips Turn Numbers Into Symbols
A virtual reel strip is a list of symbols, often 30 to 100 or more positions long, with some symbols repeated many times and others appearing once. The RNG chooses a stop position on each strip, and the symbols around that position fill the visible window.
The frequency of each symbol on the strip is what sets the odds. A simple example with a 5-reel game where the top symbol appears 2 times on a 50-position strip:
| Event | Calculation | Probability |
|---|---|---|
| Top symbol on reel 1 (one row) | 2 / 50 | 4% |
| Top symbol on the same line, reels 1 to 3 | 0.04 x 0.04 x 0.04 | 1 in 15,625 |
| Top symbol on all 5 reels, same line | 0.04 to the power of 5 | 1 in 9,765,625 |
Real games are more complex. Strips differ per reel, change during free spins, and many modern titles use variable reel heights (Megaways) or cascades. The principle stays the same: rare symbols are rare because the strip contains few of them, not because the game “decides” to hold them back.
Step 3: The Paytable Converts Symbols Into Prizes
After the reels stop, the game checks the result against its win system:
- Paylines: fixed patterns, usually left to right from reel 1. Book of Dead uses 10 lines. See how paylines work.
- Ways to win: matching symbols on adjacent reels in any row. Twin Spin uses 243 ways.
- Cluster pays: groups of touching symbols, as in Reactoonz. See cluster pays explained.
- Pay anywhere: a count of matching symbols anywhere on the grid, as in Gates of Olympus, which pays from 8 symbols.
Prizes are listed as multiples of the total bet or the line bet. If a paytable shows 5 premium symbols paying 50x the total bet and you stake A$1, that line returns A$50. Multipliers, wilds and cascades then modify the base win.
Step 4: RTP and Volatility Describe the Maths Model
The reel strips and paytable together produce two figures that describe the game:
- RTP (return to player): the share of all money wagered that the game pays back over a very large number of spins. A 96% RTP game has a 4% house edge. Over A$10,000 of total bets, the expected loss is A$400, but any single session can be far above or below that. Full detail: RTP explained.
- Volatility: how the return is distributed. Low-volatility games pay small wins often; high-volatility games pay less often and concentrate value in features and rare large wins. See pokies volatility.
Two games with the same 96% RTP can behave very differently. Starburst is a medium-volatility game with a maximum win of 800x the bet. Mental by Nolimit City is rated at the top of the studio’s volatility scale and lists a 66,666x maximum.
Step 5: Features Are Part of the Same Maths
Free spins, hold-and-win respins, multipliers and bonus buys are not extras paid out of a separate pot. Their expected value is already included in the RTP. In many high-volatility pokies, the free spins round accounts for a large share of the total return, which is why the base game can feel quiet for hundreds of spins.
Common feature types are covered on their own pages: free spins features, hold and win, bonus buy and progressive jackpots.
What Is Fixed and What You Control
| Fixed by the game | Controlled by you |
|---|---|
| RNG outcome of each spin | Stake per spin |
| Reel strips and symbol frequency | Number of spins and session length |
| Paytable and feature odds | Which game and which RTP version you play |
| House edge at a given RTP setting | Whether to use bonus buy or ante bets |
| Maximum win cap | Deposit, loss and time limits |
The right-hand column is where your decisions matter. Stake size and session length decide how much money is exposed to the house edge. Choosing a game whose casino version runs 96% rather than 94% cuts the edge from 6% to 4%, which reduces the expected loss on the same turnover by a third. Our guide to checking a game’s RTP shows where to find the figure.
How Testing and Certification Work
Before release, studios submit games to independent test labs. The lab checks that the RNG output is statistically random, that the game’s measured return over millions of simulated spins matches the declared RTP, and that the build delivered to casinos matches the certified version. Regulators then require the certified version to be used.
Online casino services offered to Australians are not licensed in Australia, because the Interactive Gambling Act prohibits providers from offering them here. Offshore casinos operate under foreign licences, so the level of checking depends on that licence. Games from large studios are usually certified for several markets, which gives some assurance about the game itself, but not about the casino’s payment practices.
Practical Checks Before You Play a New Pokie
- Open the info screen and note the RTP, volatility rating and maximum win.
- Read the paytable to see what the top symbols pay as a multiple of the bet.
- Play the free demo for 100 to 200 spins to see how often wins and features appear.
- Size your stake so your session budget covers at least 200 spins; at A$0.50 per spin that is A$100.
- Set a loss limit before you start using the casino’s limit tools.
If you want to compare places to play, our pokies sites list covers casinos accepting Australians with large game libraries.
Frequently Asked Questions
Licensed pokies from established studios use a random number generator that is tested by labs such as GLI, BMM or iTech Labs before release. They are not rigged to beat a specific player, but every game is built with a house edge, so the expected result over many spins is a loss of a few percent of turnover.
No. The outcome is fixed by the RNG at the moment the spin is requested. Quick stop or slam stop only shortens the animation; it does not change which symbols land.
No. Each spin is independent, and the RNG has no memory of previous spins. A long run without a feature does not make the next spin more likely to trigger it.
Open the info, help or paytable screen inside the game at your casino. Most studios state the theoretical RTP there, and it shows the version that casino actually runs, which can be lower than the default figure published by the studio.
The core is the same: an RNG picks outcomes and a paytable sets the prizes. The differences are in the numbers. Queensland pub machines must return 85% to 92% over their lifetime, while online pokies from major studios usually run 94% to 96.5%, and online games often have bigger feature-driven swings.
Gambling is for adults 18+ and should stay within a budget you can afford to lose. Free, confidential support is available 24/7 from Gambling Help Online on 1800 858 858.