Online slots have been at the heart of online casinos since the late 1990s. Over the years, a handful of games have stood out, not just for their graphics and gameplay, but for the way they’ve shaped the industry and captured the imagination of players around the world.

From timeless classics like Starburst to record-breaking jackpots like Mega Moolah, these games continue to dominate the scene and remain must-plays for UK slot enthusiasts.

Below, we count down the Top 10 Online Slots of All Time — and answer the most common questions UK players ask about slots and slot sites.

Top 10 Best Slots of All Time

1. Starburst

Provider: NetEnt
RTP: 96.09%
Volatility: Low

A true classic with simple gameplay, dazzling gems, and expanding wilds. Known for frequent smaller wins and a 96.09% RTP.

Play Starburst here

18+ only. Gamble responsibly — BeGambleAware.org

2. Mega Moolah

Provider: Microgaming
RTP: 88.12%
Volatility: Medium

Dubbed the “millionaire maker,” this progressive jackpot slot once paid out over £18 million to a UK player.

Play Mega Moolah here

18+ only. Gamble responsibly — BeGambleAware.org

3. Book of Dead

Provider: Play’n GO
RTP: 96.21%
Volatility: High

Rich Wilde’s Egyptian adventure slot is high-volatility, offering the chance at huge multipliers. A free spins favourite with a 96.21% RTP.

Play Book of Dead here

18+ only. Gamble responsibly — BeGambleAware.org

4. Big Bass Bonanza

Provider: Pragmatic Play
RTP: 96.71%
Volatility: Medium

A modern favourite with a fishing theme, known for its free spins round where multipliers can reel in big catches.

Play Big Bass Bonanza Here

18+ only. Gamble responsibly — BeGambleAware.org

5. Gonzo’s Quest

Provider: NetEnt
RTP: 95.97%
Volatility: Medium

The first slot to use the Avalanche mechanic, where cascading symbols replace spins. RTP 95.97%, medium to high volatility.

Play Gonzo's Quest Here

18+ only. Gamble responsibly — BeGambleAware.org

6. Bonanza Megaways

Provider: Big Time Gaming
RTP: 96%
Volatility: High

The slot that popularised the Megaways engine, offering up to 117,649 ways to win.

Play Bonanza Megaways here

18+ only. Gamble responsibly — BeGambleAware.org

7. Dead or Alive II

Provider: NetEnt
RTP: 96.8%
Volatility: High

A volatile Wild West slot, notorious for massive win potential in its free spins round.

Play Dead or Alive II

18+ only. Gamble responsibly — BeGambleAware.org

8. Cleopatra

Provider: IGT
RTP: 95.02%
Volatility: Low-Medium

The original Egyptian-themed slot, still popular both in land-based casinos and online.

Play Cleopatra here

18+ only. Gamble responsibly — BeGambleAware.org

9. Immortal Romance

Provider: Microgaming
RTP: 96.86%
Volatility: High

A gothic-themed slot with a cult following, offering multiple bonus features and character-driven gameplay.

Play Immortal Romance here

18+ only. Gamble responsibly — BeGambleAware.org

10. Thunderstruck II

Provider: Microgaming
RTP: 96.65%
Volatility: Medium

A Norse mythology-themed sequel with multiple bonus features, including the famous Great Hall of Spins, and an RTP of 96.65%.

Play Thunderstruck II here

18+ only. Gamble responsibly — BeGambleAware.org

Why These Slots Will Be Forever in the Top Most Played Slots

These slots have earned their legendary status through a combination of factors:

Big Wins: Progressive jackpots like those in Mega Moolah and Big Bass Bonanza’s interactive free spins offer players thrilling opportunities. When a slot pays it PAYS! World-record payouts in excess of £18 million just for Mega Moolah. The rest just doesn't matter, it's history! You're here to know what slot pays. What are you waiting for then?

Understanding Key Slot Features

RTP (Return to Player)

RTP represents the percentage of wagered money a slot is expected to return over time. For example, a 96% RTP returns $96 for every $100 wagered.

Volatility

Low Volatility: Small, frequent wins.
High Volatility: Bigger, less frequent wins.

Bonus Features

Interactive features like free spins, multipliers, and cascading reels add excitement and winning potential.

Types of Online Slots

Classic Slots – Traditional 3-reel slots with simple mechanics and symbols like fruits or bars.
Video Slots – Modern slots with advanced graphics and features like bonus rounds and storylines.
Progressive Jackpot Slots – Slots like Mega Moolah that offer ever-growing jackpots pooled across casinos.

Playing Slots Responsibly

Set a budget and stick to it.
Take breaks during long sessions.
Avoid chasing losses.
Use tools like the casino comparison tool to find reputable sites.

Frequently Asked Questions (UK Slot Players Ask)

What is the best UK slot site?

The best UK slot site is one that’s licensed by the UK Gambling Commission, offers fair RTP slot titles, and ensures quick, safe withdrawals. From our Top UK Online Casinos list, a strong choice is LeoVegas:

UKGC-licensed and award-winning
Huge slot library, including Starburst and Mega Moolah
Fast withdrawals with debit cards and e-wallets

Other excellent options include PlayOJO and Betway Casino — both trusted names for UK slot fans.

What is the best online slot game to win?

If you’re looking for games with the highest win potential, two stand out from our top 10 list:

Book of Dead – High volatility, with the potential for 5,000x your stake in the free spins round.
Mega Moolah – Progressive jackpot slot that has changed lives with multimillion-pound payouts.

For players who prefer steady wins, Starburst is often considered the best pick, thanks to its low volatility and frequent payouts.

What is the highest paying online slot machine?

When it comes to jackpots, Mega Moolah still leads the way, with world-record payouts in excess of £18 million.

For RTP-focused players (non-jackpot slots):

Ugga Bugga (Playtech) – 99.07% RTP
Blood Suckers (NetEnt) – 98% RTP

These titles are considered the highest paying slots online in terms of long-term returns.

What UK online casino offers the best payout?

UK casinos with the best payout reputations combine transparent RTP rates with fast withdrawals. Among our featured partners:

LeoVegas

Try LeoVegas Here

18+ only. Gamble responsibly — BeGambleAware.org

PlayOJO

Try PlayOJO here

18+ only. Gamble responsibly — BeGambleAware.org

Goldwin

Try Goldwin here

18+ only. Gamble responsibly — BeGambleAware.org

New Online Slots

Recent hits like Big Bass Splash, San Quentin 2, and Fire in the Hole showcase cutting-edge designs and features, proving the industry’s ongoing innovation.

Conclusion

From Starburst to Mega Moolah, the slots in our top 10 list aren’t just games — they’re icons of online gambling. And with UK players still searching for the best sites, highest RTPs, and biggest jackpots, these slots continue to define the industry.

Top 10 Best Online Slot Games of All Time

Choosing Between Live Dealer Games and RNG Games

The Ultimate RTP Guide: How to Find the Best-Paying Slo...

Which Casino Games Have the Best Odds? A Quick Comparis...