The Short Version
Most players assume a slot has one RTP. Many do not. Providers routinely ship a single game in several return-to-player configurations and let each casino choose which to license. The reels, the artwork and the features are identical — only the long-run return changes, and the choice is almost never advertised.
Of the 38 slots we have reviewed and verified: 5 have variant figures that are publicly documented, 19 are known to ship alternative configurations without the exact figures being public, and 14 have only one documented figure.
What the Difference Actually Costs
RTP is a long-run average, not a session prediction, so the honest way to express the gap is in expected loss over turnover rather than in any single outcome.
Cycle £2,000 through a slot — which a £1 spin reaches in 2,000 spins, an ordinary evening for many players:
| Build | Expected return | Expected loss |
|---|---|---|
| 96.50% | £1,930 | £70 |
| 94.50% | £1,890 | £110 |
| 92.00% | £1,840 | £160 |
Identical play, identical game, more than double the expected loss at the bottom build. Nothing about the interface tells you which one you are on.
The Data
Every figure below comes from our own reviews, where RTP is checked against provider documentation and cross-referenced against at least two independent sources. Where a game is known to ship variants but the exact percentages are not public, the table says so — we have not estimated them.
| Slot | Provider | Default RTP | Lower configurations |
|---|---|---|---|
| Buffalo King Megaways | Pragmatic Play | 96.52% | Variants published 94.51% |
| Fire in the Hole 2 | Nolimit City | 96.07% | Variants published 94.08%, 92.07%, 87.05% |
| Fishin' Frenzy The Big Catch 3 | Blueprint Gaming | 95% | Variants published 93%, 92% |
| Gates of Olympus | Pragmatic Play | 96.50% | Variants published 94.50%, 93.50% |
| Money Train 4 | Relax Gaming | 96.10% | Variants published 96.50% |
| Big Bass Bonanza | Reel Kingdom / Pragmatic Play | 96.71% | Variants exist Exists, figure not published |
| Big Bass Splash | Pragmatic Play | 96.71% | Variants exist Exists, figure not published |
| Book of Dead | Play'n GO | 96.21% | Variants exist Exists, figure not published |
| Book of Ra | Novomatic | 94.2% | Variants exist Exists, figure not published |
| Book of Ra Deluxe | Novomatic | 95.4% | Variants exist Exists, figure not published |
| Dead or Alive | NetEnt | 96.8% | Variants exist Exists, figure not published |
| Dead or Alive 2 | NetEnt | 96.82% | Variants exist Exists, figure not published |
| Fire Joker | ELK Studios | 95.8% | Variants exist Exists, figure not published |
| Gates of Olympus 1000 | Pragmatic Play | 96.50% | Variants exist Exists, figure not published |
| Mental | Nolimit City | 96.08% | Variants exist Exists, figure not published |
| Money Train 3 | Relax Gaming | 96.10% | Variants exist Exists, figure not published |
| Razor Shark | Push Gaming | 96.70% | Variants exist Exists, figure not published |
| Starburst | NetEnt | 96.5% | Variants exist Exists, figure not published |
| Starburst XXXtreme | NetEnt | 96.45% | Variants exist Exists, figure not published |
| Starlight Princess | Pragmatic Play | 96.50% | Variants exist Exists, figure not published |
| Sugar Rush | Pragmatic Play | 96.50% | Variants exist Exists, figure not published |
| Sweet Bonanza | Pragmatic Play | 96.48% | Variants exist Exists, figure not published |
| Sweet Bonanza 1000 | Pragmatic Play | 96.53% | Variants exist Exists, figure not published |
| The Dog House Megaways | Pragmatic Play | 96.55% | Variants exist Exists, figure not published |
| Bonanza Megaways | Big Time Gaming | 96.00% | Single figure No variant documented |
| Fluffy Favourites | Eyecon | 95.388% | Single figure No variant documented |
| Fluffy Favourites Megaways | Eyecon | 94.995% | Single figure No variant documented |
| Gonzo's Quest Megaways | Red Tiger | 96.00% | Single figure No variant documented |
| Legacy of Dead | Play'n GO | 96.58% | Single figure No variant documented |
| Mega Moolah | Microgaming | 88.12% | Single figure No variant documented |
| Money Train 2 | Relax Gaming | 96.40% | Single figure No variant documented |
| Rainbow Riches | Barcrest | 95.00% | Single figure No variant documented |
| Rainbow Riches Megaways | Barcrest | 96.00% | Single figure No variant documented |
| Reactoonz | Play'n GO | 96.51% | Single figure No variant documented |
| San Quentin xWays | Nolimit City | 96.43% | Single figure No variant documented |
| Sugar Rush 1000 | Pragmatic Play | 96.53% | Single figure No variant documented |
| Wanted Dead or a Wild | Hacksaw Gaming | 96.38% | Single figure No variant documented |
| Wolf Gold | Pragmatic Play | 96.01% | Single figure No variant documented |
How to Check Which Build You Are Playing
- Open the game.
- Find the information or paytable panel — normally a ? or i icon, sometimes inside the settings menu.
- Look for the return-to-player line. It is usually near the bottom of the rules text.
- Compare it against the default in the table above.
That figure is authoritative for that casino, because it is generated by the build actually deployed. It takes about ten seconds and it is the only reliable method — no third-party site, including this one, can tell you what a specific operator has licensed today.
What We Do Not Know
Being precise about the limits of this data matters more than making it look complete:
- We cannot tell you which build a given casino is running. That is per-operator, changes without notice, and is only visible in the game itself.
- The 19 "variants exist" entries are not quantified because the providers have not published the figures. Any site listing exact numbers for these is guessing.
- We cannot audit deployed builds. We can read what a game reports; we cannot independently verify the software matches it. No affiliate site can.
- This is not evidence of wrongdoing. Offering multiple configurations is a disclosed commercial practice, not manipulation. The criticism here is of poor disclosure, not of the mechanism.
Frequently Asked Questions
What is an RTP variant?
Many slot providers ship a single game in several return-to-player configurations and let the operator choose which to license. The game looks and plays identically; only the long-run return differs. Gates of Olympus, for example, exists at 96.50%, 94.50% and 93.50%.
Is running a lower RTP build legal?
Yes. Providers offer the configurations and operators select one. It is a disclosed commercial option, not a rigged game. The problem is that the choice is rarely advertised, so players routinely assume they are getting the headline figure.
How do I check which RTP I am playing?
Open the game's information or paytable panel — usually the ? or i icon — and look for the return-to-player line. That figure is the build actually deployed by that casino. It takes about ten seconds and is the only reliable way to know.
How much does the difference actually cost?
On £2,000 of total turnover, a 96.50% build returns roughly £1,930 in expectation and a 92% build roughly £1,840 — about £90 more lost for identical play. The gap compounds the longer you play.
Do non-GamStop casinos run lower RTP builds more often?
We have no evidence that offshore operators do this more than UK-licensed ones, and we are not going to claim otherwise. The configuration is chosen per operator in both markets. What differs offshore is that there is no UK regulator to complain to if the disclosure is poor, which makes checking the panel yourself more important.
Where does this data come from?
Each figure is taken from our own slot reviews, where RTP is verified against provider documentation and cross-checked against at least two independent sources before publication. Where a variant exists but its exact figure is not public, this page says so rather than estimating.
Full methodology, including how we test and what else we cannot verify, is on how we rank casinos. Individual game data lives on each slot review.