Two people open the same slot at two different casinos. Same artwork, same reels, same Egyptian explorer. One of them is playing a game that pays back, on paper, 12 percentage points more of what goes into it than the other.
Neither has been told which one they are on, and neither can find out by spinning. This is about that number, who chooses it, and where to read it.
One game, five builds
Studios ship many of their slots in several return-to-player configurations, and the casino picks which one goes live. The best-documented case is Play’n GO’s Book of Dead slot.
OLBG puts its default at 96.21%, which it calls the highest setting Play’n GO produces for it. The other builds sit at 94.25%, 91.25%, 87.25% and 84.18%. Same game, five prices.
Blueprint Gaming’s Eye of Horus slot does the same thing. 32Red’s review says it found five different RTPs, running from 90.25% up to 96.31%.
Nor is it an Egyptian speciality. Hacksaw Gaming’s own page for Wanted Dead or a Wild lists the RTP as “96.38%; 94.55%; 92.33%; 88.42%”. Four versions, in the studio’s own words.
What RTP is, and what it is not
RTP is a long-run average. It is what the game is designed to return across an enormous number of spins, played by everybody, over its whole life. The Gambling Commission’s own guidance calls it “the average theoretical return to player percentage”, and both of those adjectives are doing work.
It is not a forecast for your session. A 96% slot does not hand back £96 of tonight’s £100. You might lose the lot in twenty minutes, or land a feature and walk away ahead. The percentage says nothing about which.
The arithmetic, per £100
So what does the gap actually cost? Take £100 of total stakes. Not £100 deposited – £100 staked, which at 10p a spin is just 1,000 spins, winnings recycled included.
On the 96.21% build of Book of Dead, the theoretical expectation is that £96.21 comes back and £3.79 stays with the house. On the 84.18% build, £84.18 comes back and £15.82 stays. That is more than four times the expected cost for the same game.
Eye of Horus is narrower but the same shape. At 96.31% the expected cost is £3.69 per £100 staked. At 90.25% it is £9.75.
Read those numbers the right way round. They are what each build is expected to cost you, not what any build is expected to pay you. Every one of them is below 100%. Long term the house wins at every setting, and the top build just wins more slowly.
Which is also why a casino picks a lower build. We have no operator’s word on how it chooses, but the arithmetic needs no help: a lower RTP keeps more of every pound staked, on a game players already go looking for by name. Choosing by reputation is not choosing by price, and the price is the bit that varies.
How to check which version you are on
Open the game, then open its information or paytable screen before you spin. OLBG’s advice for Book of Dead is exactly that: the RTP you are playing is shown in the paytable. If you play a lot of Play’n GO slots, it is a habit worth a few seconds every time.
That is the figure for the build in front of you, not the studio’s headline. If it is well below what you expected, you have learned something about the casino, not the game.
Do UK rules make them tell you?
They do. Under the Commission’s remote technical standards, RTS requirement 3C says information enabling an “informed decision about his or her chances of winning must be easily available before the customer commits to gamble.” That must include “the return to player (RTP) percentage or the probability (likelihood) of winning events occurring”.
The guidance adds that the information may sit “in ‘help’ or ‘how to play’ pages”, or within the game. And the Commission has said, in a 2024 freedom of information response, that remote licensees must comply with the RTS under licence condition 2.3.1.
What we could not find is any requirement to tell you that a better build of the same game exists. You are entitled to the number. Nobody is obliged to mention the other four.
And no, you cannot tell by playing. A few points of RTP is pennies per pound, averaged over a vast number of spins. A single session swings by far more than that in either direction, which is the whole point of a slot.
A cold evening does not prove you were on the low build, and a hot one does not prove the high one. Feel tells you nothing. The information screen is the only honest answer.
Image: old fruit machines on Teignmouth pier, Devon, by Billy Hicks, CC BY-SA 3.0.
18+. Gambling should be entertainment, not income. Long term the house wins. Free and confidential help is at BeGambleAware.org.
