Non-GamStop Slot Sites

Slots are the largest part of the online casino market by a wide margin. On most sites they account for the overwhelming majority of the games listed, the majority of the bets placed and the majority of the revenue. Live tables get the attention and sportsbooks get the headlines, but the slot library is what most players actually spend their time on — and it is the part of a casino that is hardest to judge from the outside.

That difficulty is worth naming. A live lobby can be assessed by counting tables and checking limits. A sportsbook can be assessed by comparing prices on the same event. A slot library cannot be assessed by counting games, because the number is close to meaningless: a site with 5,000 titles from studios you have never heard of is a worse place to play than a site with 1,500 titles from the ten studios that matter. The count is the easiest thing to advertise and the least useful thing to know.

This page sets out what actually distinguishes one slot library from another — the provider mix, the volatility profile, and the RTP setting on the games you are actually going to play. That last one is the most important and the least discussed, and it is where two casinos offering the identical game can be offering you a materially different deal.

The biggest libraries

If you want the numbers anyway — and they do tell you something about the scale of the operation — these are the five largest game counts in our comparison. The spread across all ten runs from 4,000+ at Cheeky Wins down to 3,000+ at MaximalBet.

Two things to note about those figures. Published counts for the same casino vary depending on who is counting and when — a library described as “3,000+” on the operator’s own site is often listed as 3,500 or 2,800 elsewhere, because nobody agrees on whether to count demo versions, table games or titles that are temporarily unavailable. And a large count is not evidence of a good library: aggregated content from dozens of small studios can inflate a number very quickly, and most of those titles are games you will never open twice.

The most useful reading of the table above is that every casino here has a library in the low thousands at least. Past that point the count stops being a differentiator and the mix starts to matter.

How to judge a slot library

Six things, in rough order of how much they should affect your decision.

• Which studios are present. This is the single best proxy for library quality. If Pragmatic Play, NetEnt, Play’n GO, Microgaming, Nolimit City, Relax Gaming and Hacksaw Gaming are all there, the operator has real integration relationships and you will find the games you have heard of. If none of them are there, you are looking at a library built from aggregated no-name content.
• The RTP setting on the games you play. The most financially significant item on this list, and covered in full below. The same game can be deployed at different return settings and the casino chooses which.
• The volatility mix. A library that is entirely extreme-volatility games is not a library you can play a relaxed session on. The best-balanced sites carry the whole range, so you can move between low-volatility sessions and high-variance hunts on the same account.
• Bonus-buy availability. Most modern high-volatility games offer a feature you can buy outright rather than wait for. This is worth its own note, because the UK Gambling Commission prohibited the sale of bonus features at UK-licensed operators from 31 October 2021. Offshore casinos are not bound by that rule, so bonus buys — which typically cost 50x to 200x your stake per spin and carry the same RTP as the base game, or slightly less — are commonly available here. It is a genuine difference between the two markets, in both directions.
• Jackpot games. Networked progressives such as Microgaming’s Mega Moolah can reach eight figures, but the base game behind the jackpot is usually a high-house-edge slot and the odds of the top prize are very long. Local jackpots are smaller and more frequent. Check whether a jackpot is networked across an operator group or held locally — it changes both the size and the odds.

What is not on the list: the total number of games, the number of providers in the headline, and any claim about “the best slots”. Those are marketing figures.

A note on Megaways

Megaways is a game mechanic rather than a studio. It was developed by Big Time Gaming — now part of the Evolution group — and licensed to other studios, which is why you will see Megaways titles from many different providers. The mechanic varies the number of symbols on each reel on every spin, which changes the number of ways to win from spin to spin; a six-reel layout can reach 117,649 ways. In practice it means highly variable spin outcomes and, usually, high volatility. The Megaways label tells you something about the shape of the game and nothing at all about its RTP, which varies by title and by operator.

The providers that matter

There are hundreds of slot studios. A few dozen matter. These are the ones you will find at essentially every serious casino in this market, and what each of them is actually known for.

Pragmatic Play

Malta-based, founded in 2015, and the highest-volume studio in the industry by release rate — it has put out multiple new titles a month for years. The games you are most likely to meet are Gates of Olympus, Sweet Bonanza and the Big Bass Bonanza series. Volatility is mostly high, and the studio publishes maximum wins in the 2,100x to 21,100x range depending on the title. Pragmatic also runs Drops & Wins, a networked prize-drop promotion that appears across many of its games. The criticism most often made of the studio is that a lot of its output is a variation on a small number of mechanics — fair, but it is also why its games are so widely recognised.

NetEnt

Swedish, founded in 1996, one of the oldest studios in the market and part of the Evolution group since 2020. Starburst, Gonzo’s Quest, Dead or Alive 2 and the Divine Fortune progressive are the reference titles. NetEnt is known for production quality and for a broad spread of volatility rather than a house style — Starburst is a low-volatility game by any measure, while Dead or Alive 2 is famously brutal. It is also one of the studios most associated with publishing several RTP configurations of the same game, which is the subject of the next section.

Play’n GO

Swedish, founded in 2005 and based in Växjö. Book of Dead is the game that made it, and it remains one of the most widely deployed slots in the market; Reactoonz, Rise of Olympus, Legacy of Dead and Moon Princess are the other names to know. The studio is strongest on grid and cluster mechanics — Reactoonz is the clearest example — and on the “book” format that Book of Dead defined. Like NetEnt, it publishes multiple RTP variants of its catalogue.

Microgaming

Founded in 1994 and based on the Isle of Man, Microgaming is the studio that effectively built the online slot market. Much of its distribution now runs through Games Global following a 2022 restructuring, which is why the branding on newer titles can differ from the branding you remember. Thunderstruck and Immortal Romance are the legacy titles, and the Mega Moolah network is the jackpot system most often cited when a record online payout is reported. If you care about progressive jackpots, Microgaming’s networks are the ones to look for.

Nolimit City

Swedish, founded in 2014 and acquired by Evolution in 2022. San Quentin xWays, Mental, Tombstone RIP and Fire in the Hole are the titles, and the studio has built its identity on extreme volatility and signature mechanics — xWays, xNudge, xSplit — that change how the reels behave mid-spin. Maximum wins run to 150,000x on some titles, which is among the highest published anywhere. This is not a studio for a relaxed session: the hit rate is low and the swings are large. It is, however, the studio most often named when players talk about the highest-variance slots available.

Relax Gaming

Malta-based, founded in 2010. The Money Train series — Money Train 2, 3 and 4 — is the flagship, alongside Temple Tumble and Snake Arena. Relax is unusual in being both a studio and a distributor: its Silver Bullet programme brings smaller studios to market, so a game branded as Relax may have been built by someone else and released through Relax. If you like the Money Train format, you already like what Relax does best.

Hacksaw Gaming

Founded in 2018 and based in Malta, Hacksaw is the youngest studio on this list and the one that has risen fastest. It started with scratchcards before moving into slots, and the slot catalogue — Wanted Dead or a Wild, Le Bandit, Chaos Crew, RIP City — is built around very high volatility, large maximum wins and a heavy emphasis on bonus buys. If you want to understand what the modern high-variance market looks like, Hacksaw is where to start.

There are other studios worth knowing — Red Tiger, Big Time Gaming, Push Gaming, Quickspin, Thunderkick and NoLimit’s fellow Swedes in the BTG stable among them — but the seven above are the ones whose presence or absence tells you the most about a library.

Volatility explained

Volatility describes how a slot distributes its wins over time. It is not the same thing as RTP, and confusing the two is the most common mistake players make.

RTP is the average return over millions of spins. A 96% RTP game gives back £96 for every £100 staked, on average, over a very long run.

Volatility is the shape of the road to that average. A low-volatility game pays small amounts often, so your balance moves gently and a session lasts a long time. A high-volatility game pays rarely and heavily, so most sessions end with the balance gone and a minority end with a large multiple of the stake.

Two games can both have 96% RTP and feel nothing alike. The average is identical; the experience is not. That is the whole point, and it is why “which slot has the best RTP” is a less useful question than “which slot suits the session I want to have”.

Two warnings about those bands. First, there is no industry-wide scale. Pragmatic Play publishes a volatility rating of its own, Nolimit City uses its own language, and a “high volatility” label from one studio is not equivalent to the same label from another. Any table like the one above, including this one, is an approximation built from published maximum wins and observed behaviour, not a standard.

Second, volatility is not a strategy. It does not change the expected return, and no sequence of volatility choices turns a negative-expectation game positive. What it changes is the probability of a long session versus a short one. If your bankroll is £50, playing a 150,000x-maximum Nolimit City title at £1 a spin is a decision to probably lose the £50 quickly. If your bankroll is £50 and you want an evening’s play, a low-volatility game is the only sensible choice — and even then, the house edge is still working against you every spin.

There is a practical tool here that costs nothing: almost every slot can be opened in demo mode before you stake real money. Twenty minutes in demo tells you more about whether a game’s volatility suits you than any rating does.

RTP and why it varies

This is the most important thing on this page and the one most players never find out. The same slot, with the same name and the same graphics, can be running at different return-to-player settings at two different casinos. The studio builds the game with several RTP configurations; the operator chooses which one to deploy.

A game published at 96% can also exist at 94%, and in some cases below 90%. The difference is not cosmetic. A 2% lower RTP means 2% more of every pound staked is retained by the house over time. Put against a welcome bonus worth £100 with 40x wagering, a 2% RTP difference is worth more than the bonus — and it keeps applying after the bonus is gone.

How much this affects you depends on the operator. The figures below are the ones most widely published for these titles; the lower settings are reported by third-party game databases rather than announced by the studios, so treat them as indicative.

There is a second source of variation that is easier to miss: the RTP can differ by market even within the same operator, because some jurisdictions impose minimums and others do not. The UK Gambling Commission requires operators it licenses to make the RTP available to players, and UK-licensed sites generally display it in the game’s information screen. Offshore casinos are not bound by that requirement, although in practice many still show it because the game itself does.

One qualification, because this is often overstated elsewhere. A lower RTP setting does not mean the game is rigged, and it is not evidence that an operator is dishonest. It is a commercial parameter, disclosed in the game, chosen by the operator in the same way it chooses its bonus terms. The reasonable response is not alarm but a habit: check the figure, and if the operator is running the cheap version of the games you play, factor that into where you deposit. The same logic applies to how the operator weights games towards bonus wagering, which we cover on the no wagering casinos page.