Greentube Slots: Where to Play Book of Ra in the UK

By Jack Henshaw, Head Writer · Published 4 July 2026 · Last updated 9 July 2026

Greentube is the digital arm of an Austrian arcade empire so large it barely needs online slots to matter: Novomatic, founded by Johann Graf in 1980, now runs 2,000+ gaming venues (many under the Admiral brand) across 50 countries. Greentube’s own 1998 Vienna start-up gave that empire its online voice — and gave the whole industry Book of Ra, the game that invented the “Book” genre every provider on this site now ships a version of. Our verdict: 7.5/10. This Greentube review covers the best Greentube slots ranked, the genre Book of Ra founded, and the full licence file.

Where to Play Greentube Slots

Greentube at a glance

The essentials — a five-entity UK licence estate that mirrors a genuinely continental business.

✓ Facts checked against the UKGC business licence register and Novomatic’s published data — 4 July 2026

The best Greentube slots: 9 games that actually matter

Four hundred games, nine places — a shorter list than most of our reviews, because Greentube’s genius was concentrated in a handful of Austrian arcade classics rather than spread across a modern release calendar. RTPs quoted are typical online defaults. The full ranked catalogue is near the end of the page.

1. Book of Ra Deluxe (2005)

The game that invented an entire genre: an Indiana Jones-adjacent explorer, a golden book scatter, and a special expanding symbol chosen at random during free spins that can fill an entire reel. Simple to the point of severity by modern standards — no cascades, no megaways, no multiplier ladders — and imitated more than almost any slot in history: every “Book of” title from every studio on earth, Play’n GO’s Book of Dead included, is negotiating with this design. Published default around 95.1% on the Deluxe build; the original 2005 version and its many market variants run leaner still. Continental Europe’s most-played slot for the better part of two decades.

2. Sizzling Hot Deluxe (2005)

The definitive featureless fruit machine of the online era: five reels of sevens, stars, melons and grapes, no bonus round, no free spins beyond scattered stars — just pure symbol-matching arithmetic at whatever stake the player chooses. Its total absence of modern furniture is precisely the point: for millions of continental European players raised on Admiral arcade cabinets, this is what a slot machine is. Published default around 95.66%. Astonishingly durable for a game with nothing to hide behind.

3. Lucky Lady’s Charm Deluxe (2006)

The trinity’s third pillar: a four-leaf-clover fortune slot whose free games pay out at triple the normal rate for their duration — a straightforward, honestly-labelled multiplier the whole continent came to trust. Scatter-triggered and gamble-ladder equipped in the classic Novomatic style, it rounds out the three games (alongside Book of Ra and Sizzling Hot) that most defined 2000s European online gambling before Britain’s volatility studios existed. Published default around 95.15%.

4. Lord of the Ocean (2010)

Poseidon takes the Book of Ra formula underwater: the same expanding-symbol free-spins engine, this time with a trident-wielding sea god standing in for the explorer. It proved the studio’s founding mechanic could travel to any theme without losing its audience, and remains one of the catalogue’s most requested classics outside the original trinity. Published default around 95.1%.

5. Columbus Deluxe (2010)

The Age of Exploration gets the same treatment: a compass-and-caravel scatter, expanding wilds in the free games, and the trinity’s DNA visible in every symbol choice. Less famous than Book of Ra but a steady earner across two decades of continental casino floors and online lobbies alike — the studio’s formula proving, again, that theme is decoration and the engine is the product. Published default around 95%.

6. Katana (2000s)

The samurai entry in the Novomatic arcade canon — a stern warrior scatter, expanding wilds through the bonus, and the same unmistakable early-2000s Austrian cabinet feel that Sizzling Hot and Lucky Lady’s Charm carry. A minor classic outside the trinity, but a genuine one: still requested by name on forums that remember Admiral-branded machines fondly. Published default around 95%.

7. Ultra Hot Deluxe (2010s)

Sizzling Hot’s fierier sibling: the same featureless five-reel fruit-machine grammar with a slightly hotter paytable and the studio’s familiar gamble-ladder risk option after every win. It exists to prove a point the whole catalogue makes implicitly — that the fruit-machine format never actually needed replacing, just refining. Published default around 95.7%.

8. Apollo God of the Sun (2010s)

Greek mythology joins the Book family: Apollo’s chariot scatter and an expanding wild through the free games give the formula its most dramatic art direction — sun flares, mythic architecture, a genuinely handsome cabinet-era palette. It shows the studio wasn’t incapable of visual ambition, only that it consistently chose restraint in the mechanics underneath. Published default around 95%.

9. Dolphin’s Pearl Deluxe (2010)

The gentlest entry in the canon: an underwater scatter-and-expanding-wild game whose soft blues and dolphin mascot made it a particular favourite among players who found Book of Ra’s desert too severe. Proof that the studio’s one true engine could be dressed calm as easily as it could be dressed adventurous. Published default around 95%.

Greentube vs the studios it competes with

Greentube’s fight isn’t for online-native novelty — it’s for the continental-European mainstream the volatility studios never fully cracked. Against our previously reviewed studios:

The honest read: Play’n GO’s Book of Dead is the genre’s global commercial champion, but Greentube built the genre’s actual foundation — the family resemblance is undeniable once you know to look. Against IGT and Light & Wonder, Greentube plays the same arcade-to-online role but for a different continent: where they own American and British floors, Novomatic’s Admiral empire owns Central and Eastern Europe. Aristocrat Interactive completes the set from Australia, another land-based giant whose Buffalo and Lightning Link cabinets are only now getting the same online treatment Greentube gave Book of Ra two decades ago. Nobody on this table publishes leaner defaults, and nobody else can claim to have started the whole Book conversation. One further comparison worth making even though it’s not a corporate relative: Amatic Industries, another Austrian studio with its own decades-old land-based cabinet business, ships a visibly similar Book-of wild/scatter mechanic and gamble-ladder finish — reviewers regularly note the resemblance, though the two companies are independently owned and there’s no confirmed corporate link between them. Synot Games, the Bratislava-based digital arm of the Czech SYNOT Group, rounds out this land-based-heritage cluster with its own Book-of-style engine, though its 2016 studio launch makes it a much later entrant into online slots than Greentube’s 1998 start.

The game families, in depth

A catalogue built on one engine, deployed across many themes. The full ranked list covers the rest.

The founding trinity

Book of Ra (2005) → Sizzling Hot (2005) → Lucky Lady’s Charm (2006), each subsequently given a “Deluxe” remaster — the three games that defined a decade of continental European gambling before Britain’s online-native studios existed. Between them they established the two templates — expanding-symbol Book adventure and featureless fruit machine — that the rest of the catalogue simply re-skins.

The Book expansion

Lord of the Ocean, Columbus Deluxe, Apollo God of the Sun, Katana and dozens more — all running Book of Ra’s core mechanic (scatter trigger, random expanding symbol, free spins) under different mythologies and geographies. It’s the industry’s first great example of a studio finding one engine and mining it exhaustively rather than inventing a new one every year.

The fruit-machine wing

Sizzling Hot Deluxe, Ultra Hot Deluxe and the wider “Hot” family — deliberately featureless five-reel classics whose whole appeal is the absence of modern furniture. This wing has aged the least of anything in the catalogue precisely because it never chased trends. The DNA travels: Malta independent Playson’s Fruit Crown and Sizzling Crown carry the same featureless-reel grammar, decades after Greentube proved the format never needed replacing.

The land-arcade catalogue

Beneath the online-famous shelf sits hundreds of titles built primarily for Novomatic’s own 2,000+ Admiral-branded venues — games most UK players will never encounter, playing continuously across Central European arcades, exactly as Book of Ra once did before it crossed online.

Signature mechanics & technology

Greentube’s toolkit is deliberately narrow — the studio perfected two ideas rather than chasing many:

The Book engine

A scatter book triggers free spins; at the start of the round, one symbol is randomly chosen to become an expanding wild for the whole feature’s duration. It sounds almost too simple to have founded an industry, and yet: Play’n GO’s Book of Dead, countless “Book of” titles from studios worldwide, and the entire modern “expanding symbol adventure” sub-genre all trace their lineage directly to this 2005 Austrian design.

The gamble ladder

A near-universal Novomatic feature: after any win, double-or-nothing on a card-colour or suit guess, stackable multiple times. It’s pure land-arcade DNA — the risk-it button was standard on Admiral cabinets long before online slots existed, and Greentube ported it faithfully rather than replacing it with modern bonus-buy mechanics.

Featureless volatility

Sizzling Hot and its siblings prove a design point most modern studios have forgotten: a slot needs no bonus round at all if the base-game symbol economy is tuned correctly. It’s the purest surviving expression of pre-features slot design, still commercially viable two decades on.

Land-to-online fidelity

Unlike studios that redesign land hits for online audiences, Greentube’s conversions are strikingly faithful to their arcade originals — same pacing, same restraint, same visual language. That fidelity is why the games feel dated to online-native players and comfortingly familiar to everyone who grew up near an Admiral cabinet.

Greentube slots RTP: the real numbers

The defaults: Greentube publishes some of the leanest headline figures on this entire site — typically 92–95.7% depending on title and market, with the founding trinity clustering around 95–95.7% at their online “Deluxe” builds and several land-originated titles running lower still. This isn’t an accident of translation: continental European land-arcade economics have always run leaner than the UK online market’s 96%+ norms, and Greentube’s online catalogue largely preserved that inheritance rather than adjusting upward.

The builds: the variance is real and significant — Book of Ra alone exists in a dizzying number of market-specific configurations (the original, the Deluxe, the “6” and “10” paylines editions, country-specific RTP tiers), and operators choose which one they run. The paytable check that applies everywhere on this site matters most here: assume nothing about which Book of Ra you’re actually playing.

Volatility and ceilings: generally gentle-to-medium by design, tuned for long sessions on modest stakes rather than five-figure multiplier chases — Book of Ra’s expanding-symbol jackpot moments are its most dramatic events, and even those pale against the volatility studios’ ceilings. The leaner RTPs mean sessions drain faster than the headline percentage alone suggests; our responsible gambling guide is worth reading before any extended play here.

From Gumpoldskirchen to the Book genre

The arc that matters: a small Vienna start-up built two ideas so well in 2005 that they still define a genre and a country’s gambling culture, got bought by the arcade conglomerate whose cabinets inspired those ideas in the first place, and has spent the two decades since mostly refining rather than reinventing. Few studios anywhere have shipped less change to more lasting effect.

The people who built Greentube

Johann Graf — the empire builder

Graf founded Novomatic in 1980 and built it, arcade cabinet by arcade cabinet, into one of the largest gaming-technology companies on earth — 2,000+ venues across roughly 50 countries, the Admiral brand a fixture of Central and Eastern European high streets much as bookmakers are in Britain. Greentube’s 2010 acquisition wasn’t a diversification; it was Graf’s empire finally buying its own internet address.

The Vienna founders

Greentube’s 1998 founding team built an independent online-gaming business in a Vienna that had barely heard of internet casinos, and within seven years produced Book of Ra and Sizzling Hot — two designs so foundational that every “Book” slot and every featureless classic-fruit revival made since owes them an uncredited debt. Their restraint, not their ambition, is the legacy: two ideas, executed once, correctly.

The Novomatic stewardship

Since 2010, Greentube has operated as Novomatic’s digital arm rather than an independent creative house — a deliberately conservative custodianship that has protected the founding trinity’s continued dominance rather than chasing the volatility-studio arms race. Day-to-day leadership passed to a second generation in 2019, when Thomas Graf — Johann Graf’s son, who joined the studio as CTO back in 2011 — was appointed CEO, formalising a family succession that runs through the wider Novomatic group too (Johann Graf began transferring ownership stakes to Thomas in 2021). It’s a strategy that reads as under-ambitious to online-native eyes and as sensible brand stewardship to anyone who has watched the trinity outlast three generations of “innovative” rivals — though under Graf’s tenure the studio has quietly kept shipping new branded families such as Piggy Prizes, Cash Connection and Diamond Link rather than standing entirely still.

Is Greentube fair? Licensing, regulation & the record

Checked against the Gambling Commission’s business licence register on 4 July 2026.

The licences. An unusually wide UK estate reflecting Greentube’s genuinely pan-European structure: Greentube Alderney Ltd holds account 39050 (remote casino, bingo, software and betting host licences, active since 2014); Greentube I.E.S GmbH holds 41020 (remote software, active since March 2015); Greentube Gibraltar Ltd holds 43091 (remote software and game host, active since 2015–17); Greentube UK Ltd holds 48666 (remote software and machine-technical, active since 2017); and parent NOVOMATIC AG itself holds a direct group licence, 45352 (remote and non-remote software and machine-technical, active since 2018–19). A predecessor entity, Novomatic Gaming Industries GmbH (2535), surrendered its older machine-technical licences in 2019 as the modern estate consolidated. Verify all on the UKGC public register.

The record. Clean across the modern estate: no UKGC enforcement action against any active Greentube or Novomatic entity that we can find. The 2019 surrender of the older Novomatic Gaming Industries licences reads as routine corporate consolidation rather than any compliance issue — the group simply moved its UK supply onto newer, more appropriately structured entities.

Beyond the UK. The same catalogue is also certified under Greentube’s own Malta Gaming Authority licence (Type 1 Gaming Services, authorisation MGA/CRP/120/2006) alongside further regulated markets the studio lists on its own compliance pages — a genuinely pan-European certification footprint that matches its pan-European licence estate.

So is it fair? Yes — certified RNG across the catalogue, five active UK licences with clean histories, and published RTP figures for every title. The caveat that matters most here isn’t regulatory but mathematical: this is the leanest published-RTP catalogue on this site, and the founding trinity in particular circulates in numerous market-specific builds. Reading the paytable before playing is advisable everywhere; on Book of Ra, it is essential.

The biggest Greentube wins

A studio built on modest, patient maths rather than lottery-scale ceilings — its records are cultural rather than record-book. Documented context only:

On tape: a Book of Ra Deluxe 10 session with the ancient power unlocked, and Sizzling Hot Deluxe doing what it has always done:

Videos embedded for illustration — results shown are the players’ own, and most Book of Ra sessions end well short of a full expanding reel.

Beyond the reels

The corners of the story the ranking competitors never reach:

The genre nobody credits properly

Ask most players who invented the “Book” slot genre and you’ll hear Play’n GO’s Book of Dead — the commercially dominant global version. The actual answer is a Vienna studio’s 2005 release that most of those players have never directly played. Greentube is arguably the most influential provider on this entire site relative to its modern name recognition.

The other Europe

British online-slot culture, shaped by NetEnt, Pragmatic and the volatility studios, is only half the story. Central and Eastern Europe’s gambling culture ran on Admiral-branded arcade cabinets and Greentube’s Book/Sizzling Hot duopoly for a full generation, largely invisible to UK-focused coverage. This page is one of the few English-language resources that treats that continent’s formative slots seriously.

Restraint as a strategy

Every other provider on this site has a section about mechanical invention — Megaways, GigaBlox, Colossal Reels, Tumbling Reels. Greentube’s equivalent section is short because the studio deliberately chose not to chase that arms race after 2010, protecting two working ideas rather than manufacturing new ones annually. Whether that reads as admirable discipline or missed opportunity depends entirely on which decade of slots you learned the hobby in.

The Admiral bridge

Uniquely among the online studios on this site (bar Light & Wonder and IGT’s land estates), Greentube’s games still run in real time on thousands of physical Admiral cabinets across continental Europe — a living bridge between the arcade-hall era and the smartphone era that most of this site’s subjects abandoned decades ago.

New Greentube slots: what’s launched for 2025–26

The state of Greentube right now: the founding trinity still anchors the studio’s reputation, but the modern release calendar is busier than that reputation suggests — Greentube’s own new-releases catalogue lists a steady drip of fresh branded titles through 2025 and 2026, concentrated in jackpot-ladder and cash-collect families rather than the volatility-studio mechanics found elsewhere on this site. This section refreshes with any significant confirmed launch.

All ship with published figures, and market build variance remains the single most important thing to check before playing. Paytable first, always.

What players actually say

From forums that skew notably more continental European than most of this site’s subjects — our words, cons intact.

The love: nostalgia, overwhelmingly — Book of Ra and Sizzling Hot are discussed the way British players discuss Fishin’ Frenzy or Cleopatra: not as games to be evaluated on modern feature checklists, but as fixtures of personal gambling history. The featureless simplicity of Sizzling Hot draws genuine praise from players exhausted by bonus-buy inflation elsewhere, and the studio’s honesty about what its games are (no false promise of megaways drama) earns quiet respect.

The gripes, plainly: the RTPs, loudly and consistently — the maths-literate corner of the community regards Greentube’s 92–95% defaults as the steepest standing tax among tier-one providers, and the proliferation of market-specific Book of Ra builds (originals, Deluxe, 6, 10, country variants) is criticised as deliberately confusing. Volatility players find the entire catalogue toothless, the visual presentation is routinely called dated even on the “Deluxe” remasters, and the post-2010 release calendar draws “stuck in 2005” complaints. All fair — and the trinity’s core audience has never once asked for a Megaways edition.

Which Greentube slot should you play?

The thirty-second version of everything above:

Our verdict on Greentube

Slot Providers score: 7.5/10 — the genre founder: Book of Ra’s influence on modern slots is enormous and under-credited, backed by a genuine continental arcade empire — docked for the leanest maths and the least mechanical ambition among our tier-one providers.

Greentube suits players who grew up on continental European gambling culture, genre historians, and anyone who wants proof that a slot needs neither cascades nor Megaways to matter. Look elsewhere if you want generous modern maths — Relax, Push and Play’n GO all publish meaningfully friendlier defaults — or mechanical novelty, where Yggdrasil and Big Time Gaming live. And whichever Book you open: check which market build you’re actually playing before you start.

Every Greentube slot that matters, ranked

From a 400-plus catalogue built overwhelmingly on two engines, the entries that matter, ranked by all-time greatness — craft, influence, maths and staying power blended.

Ranked 4 July 2026 from a catalogue of 400+ titles concentrated around the Book and featureless-fruit engines. Availability and RTP build vary enormously by market — check every time, especially on Book of Ra.

Casinos with Greentube Games

Greentube’s UK presence is real but narrower than its continental European footprint. The Greentube casinos below are a cross-section of well-known UKGC-licensed operators carrying the catalogue (listed for information only — no commercial relationship, no endorsements; verify any operator on the Gambling Commission register before depositing):

Checked 4 July 2026. Game availability and RTP builds change — always confirm in the casino’s own lobby and the in-game paytable. 18+, please gamble responsibly.

Sources & Verification

Primary sources checked 4 July 2026, re-verified and expanded 9 July 2026: the Gambling Commission’s business licence register (accounts 39050, 41020, 43091, 48666 and 45352, plus the surrendered predecessor 2535); Greentube’s official site, including its About Us page, management page and new releases catalogue; and Novomatic AG’s published corporate materials. RTPs and mechanics from the games’ published information screens. Imagery from official promotional assets and documented gameplay. Spotted an error? Tell us — corrections are actioned as a priority.

✓ Updated 9 July 2026: added Thomas Graf’s role as CEO (Johann Graf’s son, in post since 2019) to the founders and history sections, corrected the “New Greentube slots” section with real named 2025–26 releases (Piggy Prizes: Wish of Riches 2, Cash Connection – Charming Lady’s Boom Coins, Rumble Riches – Haulin’ Gold, Firecracker Frenzy – Money Toad and the upcoming Highway to Bell Stack & Collect) sourced from Greentube’s own new-releases page, added the founding detail of Ski Challenge developer Dürrschmid&Reisinger OEG before the 2000 rebrand, added the Malta Gaming Authority certification detail, added a pros/cons verdict block with matching schema, expanded the UK-availability FAQ with named casinos, moved the on-page navigation up under the ads module, and removed a duplicated family banner image.

Greentube FAQs

Who owns Greentube?

Novomatic AG, the Austrian gaming-technology group founded by Johann Graf in 1980. Greentube was founded independently in Vienna in 1998 and acquired outright by Novomatic in 2010.

Is Greentube fair, or are its games rigged?

Greentube holds five active UK licences with clean histories, certified RNG throughout its catalogue, and publishes RTP figures for every title. The honest caveat is mathematical, not ethical: its 92–95.7% defaults are the leanest published figures on this site, and Book of Ra circulates in numerous market-specific builds — check the in-game paytable every time.

What is the best Greentube slot?

Book of Ra Deluxe is the genre-defining original, Sizzling Hot Deluxe the purest featureless classic, and Lucky Lady’s Charm Deluxe the trinity’s honest tripled-spins pick. Our full ranked nine, with reasoning, is above.

Did Greentube really invent the Book slot genre?

Yes — Book of Ra (2005) established the scatter-triggered, randomly expanding-symbol free-spins format that every subsequent “Book of” title, including Play’n GO’s globally dominant Book of Dead, follows.

What RTP is Book of Ra?

It varies significantly by build and market — the Deluxe edition commonly publishes around 95.1%, but originals, paylines variants (6 and 10) and country-specific configurations all differ. The in-game paytable states the build you’re actually playing.

What is Novomatic, and how does it relate to Greentube?

Novomatic is the parent company — an Austrian gaming-technology group operating 2,000+ venues (many under the Admiral brand) across roughly 50 countries. Greentube is its dedicated online-gaming division.

Why does Sizzling Hot have no bonus features?

By deliberate design — it’s a featureless five-reel fruit machine whose entire appeal rests on tuned base-game symbol economics, a land-arcade design philosophy Greentube preserved faithfully when bringing the game online.

What is the gamble ladder feature?

A near-universal Novomatic mechanic: after any win, players can risk it on a double-or-nothing card guess, repeatable multiple times — inherited directly from Admiral land-based cabinet design.

Are Greentube slots available in the UK?

Yes, through five active UKGC-licensed entities, though the catalogue’s UK footprint is narrower than its dominance across continental Europe. Videoslots, Unibet and bet365 Casino are among the UK-licensed lobbies we’ve found carrying the Book of Ra/Deluxe shelf — see the full UK casinos section above for the honest breakdown.

Is Greentube still releasing new slots?

The studio’s modern output is conservative compared to online-native rivals — primarily market-specific builds and paylines editions of the founding trinity, plus periodic crossovers from Novomatic’s land-based Admiral catalogue.