Microgaming created some of the most famous online slots, including Mega Moolah, Thunderstruck II and Immortal Romance. Since 2022 these games have been run by Games Global, which bought Microgaming’s games portfolio and distribution business, but many players still know them as Microgaming slots. This page lists the games reviewed on UnionSlots with their RTP, volatility and max win and covers the UK rules that apply when you play them. UnionSlots does not host games or demos; we review slots and point you to UKGC-licensed casinos. 18+ only.
Where to Play Microgaming Slots in the UK
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1
Get 200 FS on Book of Dead with £20 Min Deposit
#AD | Automatically credited upon deposit. First Deposit Only | Min dep. £20. Game: Book of Dead | Spin Value: £0.1. Max Free Spins: 200. WR 10x free spin winnings amount (only Slots count) within 30 days | Max bet is 10% (min £0.10) of the free spin winnings amount or £5 (lowest amount applies) | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
2
Get 100% up to £50 + 50 Free Spins on Book of Dead
#AD | First Deposit Only | Min. deposit: £10, max. Bonus £50 | Game: Book of Dead | Spin Value: £0.1, Max Free Spins: 50 | WR of 10x Bonus amount and Free Spin winnings amount (only Slots count) within 30 days | Max bet is 10% (min £0.10) of the free spin winnings and bonus amount or £5 (lowest amount applies) | Spins must be used and/or Bonus must be claimed before using deposited funds. Bonuses do not prevent withdrawing deposit balance | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
3
Get 200% up to £50 + 20 Free Spins on Book of Dead
#AD | New Players Only. Wager from real balance first | 10X wager the bonus money within 30 days, and 10x wager any winnings from the free spins within 7 days | Contribution varies per game | Available on selected games only | Wager calculated on bonus bets only | Bonus offer and any winnings from the offer are valid for 30 days / Free spins and any winnings from the free spins are valid for 7 days from receipt | Max conversion: £50 the bonus amount or from free spins: £20 | Min Deposit £10 required | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
4
Get 100% up to £50 + 100 FS
#AD | New Players Only | Wager from real balance first. 10X wager the bonus money within 30 days and 10x wager any winnings from the free spins within 7 days | Contribution varies per game | Available on selected games only | Wager calculated on bonus bets only | Bonus offer and any winnings from the offer are valid for 30 days / Free spins and any winnings from the free spins are valid for 7 days from receipt | Max conversion: from the bonus amount: £50 or from free spins: £20. Min Deposit £20 required. Limited to 5 brands within the network | Withdrawal requests void all active/pending bonuses | Excluded Skrill and Neteller deposits | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
5
Get £100 Bonus + 100 Free Spins
#AD | New customers only. Opt-in required. Offer valid for 7 days from account registration Match Deposit Bonus Terms: 100% Match Bonus up to £100 on 1st deposit of £20+. 10x bonus wagering applies as do weighting requirements. Debit Card deposits only. Irregular gameplay may invalidate your bonus. Free Spin Terms: 100 Spins awarded on Big Bass Bonanza, valued at 10p per spin. | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
6
Get £100 Bonus + 100 Free Spins
#AD | New UK based customers only. You must opt in (on registration form) & deposit £10+ via a debit card to qualify. Offer valid 7 days from registration. Welcome Bonus: 100% match up to £100 on 1st deposit. 10x wagering applies (as do weighting requirements). Free Spins: Awarded on Gold Blitz once you have staked £10 on any game. Spin value = 10p. No wagering requirements on free spin winnings. | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
7
Get 100 FS with a £10 Deposit (Wagering Required)
#AD | Welcome bonus for new players only | Selected game: Big Bass at the Races | Deposit & wager at least £10 to get free spins | Free Spins winnings are cash | No max cash out | Eligibility is restricted for suspected abuse | Skrill deposits excluded | Free Spins value £0.10 per spin | Free Spins expire in 48 hours | T&C's apply | 18+ | BeGambleAware.org | Gambling is addictive, please gamble responsibly!
Best Microgaming Slots by RTP
Default RTP as shown in our reviews; many games come in several RTP versions, so check the information screen at your casino. A dash means no reliable max win figure is published.
| Slot | Default RTP | Volatility | Max win |
|---|---|---|---|
| Immortal Romance | 96.86% | High | 12,150x |
| Thunderstruck II | 96.65% | High | 8,000x |
| Mermaids Millions | 96.56% | Medium | — |
| Starlight Kiss | 96.52% | Medium | — |
| Book of Oz | 96.31% | Very high | 5,000x |
| Thunderstruck | 96.10% | Medium | 3,333x |
| Mega Moolah | 88.12% | Low | Progressive jackpot |
Microgaming Slots Reviewed on UnionSlots
- Mega Moolah: the progressive jackpot slot whose Mega jackpot starts at £1 million
- Thunderstruck II: 243 ways and the Great Hall of Spins, where better free spins levels unlock the more often you reach the bonus
- Immortal Romance: 243 ways, the Wild Desire feature and character-based free spins
- Thunderstruck: the 9-line original of the series, with free spins and a gamble feature
- Book of Oz: a very high volatility book slot with free spins and expanding symbols
- Mermaids Millions: an underwater slot with a bonus pick game and free spins
- Starlight Kiss: a medium-volatility slot with bonus rounds and free spins
About Microgaming and Games Global
Microgaming was founded in 1994 on the Isle of Man and was one of the first developers of online casino software. In 2022 it sold its games portfolio and distribution business to Games Global, which now runs Mega Moolah, Thunderstruck II and Immortal Romance and releases new games from its partner studios, while Microgaming itself focuses on platform, licensing and compliance services. Microgaming introduced the 243 ways to win format in 2009 with Burning Desire; Thunderstruck II followed in 2010 and Immortal Romance in 2011, and a sequel, Immortal Romance 2, came out in 2024.
Mega Moolah Jackpots
Mega Moolah’s progressive jackpots are won through a jackpot wheel that is triggered at random. The Mega jackpot starts at £1 million and has paid record sums: £13.2 million in October 2015, a Guinness World Record at the time, then €18.9 million in 2018 and €19.4 million in 2021. Its default RTP of 88.12% is much lower than in most slots, so the game suits players chasing the jackpot rather than steady returns.
Playing Microgaming Slots in the UK
All the Microgaming slots we review run in the browser on desktop and mobile. At UKGC-licensed casinos the maximum stake on online slots is £5 per spin (£2 if you are 18–24), autoplay and turbo spins are switched off and bonus buys are not offered. Demo mode is available at most licensed casinos once you have registered and verified your age. For another big jackpot series, see our Playtech slots with Age of the Gods.
Gambling Responsibly
Set a budget before you play and treat slots as paid entertainment. If gambling stops being fun, GamCare (National Gambling Helpline 0808 8020 133, 24/7) and GamStop offer free, confidential help.
FAQ
Who owns Microgaming slots now?
Since 2022 Microgaming’s games portfolio, including Mega Moolah, Thunderstruck II and Immortal Romance, has belonged to Games Global. Microgaming itself now focuses on platform, licensing and compliance services.
How much is the Mega Moolah jackpot?
The Mega jackpot starts at £1 million and grows until it is won. The biggest wins so far include £13.2 million in 2015 and €19.4 million in 2021.
What are the best Microgaming slots?
Mega Moolah, Thunderstruck II and Immortal Romance are the studio’s best-known games in the UK. Immortal Romance has the highest default RTP of the titles we review, at 96.86%.
What RTP do Microgaming slots have?
Most of the games we review have default RTPs between 96.1% and 96.9%; Mega Moolah is the exception at 88.12%. Many titles come in lower versions too, so check the information screen at your casino.
Can I play Microgaming slots for free?
UnionSlots does not host demos. UKGC-licensed casinos can offer demo mode once you’ve registered and verified your age (18+).