20+ years in the gambling industry including 13+ years playing and reviewing slots.
With so many slot games to choose from, the ones that stand out are the ones with the best bonus features. Known as bonus slots, a bonus feature can either make or break a game and determine its popularity with players.
Whilst a free spins feature is the most common bonus feature, times have changed with studios now creating complex and innovative bonus features to capture our attention. The slots with the best bonus features are the ones that occupy the top positions at UK slot sites and rightly so.
In OLBG’s ultimate guide to the best slots for bonus hunting, we look at the most popular bonus features, which ones trigger more frequently and which ones offer the biggest payouts.
The Best Bonus Slots Features in the UK
With thousands of slot games to choose from, it’s hard to know where to begin. The slot games found at the top of slot sites is a good indication what is popular with players and this is evident through their no wager free spins offers. Below, you’ll find 7 of the best bonus slots. Before scrolling on, you can find links for detailed reviews as well as free slot demos where you can sample all the bonus features:
1. Big Bass Bonanza
Released in December 2020 and the first game in the series, Big Bass Bonanza is appealing to players for many reasons. With a fun fishing theme, many sites have free spins offers on this iconic game. Played on 5 reels and 10 paylines from 10p per spin, a major reason why it’s a popular bonus slot is due to the Free Spins feature.
The Fisherman Wild comes into pay and collects Fish Money symbols on the reels. Fisherman Wilds also award additional free spins and increase the multiplier up to 10x which then applies to Fish Money symbols collected. With a high 96.71% RTP rate and 2,100 x bet max wins, you’ll trigger the Free Spins feature every 113 free spins on average.
2. Big Bass Splash
The fifth game in the series, Big Bass Splash is similar to Big Bass Bonanza. Also played on 5 reels and 10 paylines from just 10p per spin, the Free Spins feature is also played every 113 spins on average. Theoretically, it’s easy to trigger the feature with random extras in the base game.
Importantly, Pragmatic Play has added up to 5 modifiers before the feature begins. This includes more fish money symbols on the reels, more Fisherman Wilds, beginning at level 2 with a 2x multiplier, extra free spins and a higher chance of activating random extras. Finally, Big Bass Splash comes with the same 96.71% RTP rate but higher 5,000 x bet max win potential.
3. Starburst
One of the most popular slot games ever, NetEnt’s Starburst is a classic among classics. With 5 reels and10 paylines, this simple outer space-themed juggernaut can be played from just 10p per spin. The focus is on the Starburst Wild symbol which lands on any of the 3 central reels. When it does, it expands to give you a wild reel and free re-spin.
If more Starburst Wilds land, you’ll get another wild reel with another re-spin. With the possibility of 3 wild reels and Win Both Ways technology, wins of up to 500 times your total bet are possible on each spin/re-spin. Hypnotic and mesmerising, a Starburst Wild symbol will land every 11.9 spins which makes it perfect for bonus hunting.
- Great selection of leading slots
- Trusted UK operator
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4. Book of Dead
Play ‘n GO’s Book of Dead is also up there as it’s been the subject of many a casino’s welcome offer. With an ancient Egyptian theme, this 5 reel, 10 payline game is all about the Free Spins feature. What draws players in is that a special expanding symbol is chosen before the feature begins.
When this symbol appears, it expands to take over the whole reel. The more reels it appears on, the bigger the win potential. If a high-value symbol is chosen, wins of up to 5,000 x bet can be won on every free spin. What makes Book of Dead’s bonus feature so engaging is the hope you’ll land Rich Wilde as the special expanding symbol. This is the reason why ‘Book of’ slots are so popular.
- Full Range of Live Casino Options
- Free Spins Bonuses for Regular Players
- Easy Switching from Sports to Casino and Vice Versa
5. Bonanza Megaways
Created by Big Time Gaming, Bonanza Megaways is the game that put Megaways on the map. With 6 reels and up to 117,649 ways to win, this mining-themed slot sees you dig for gold. With Reactions awarding continuous spins, the focus is the Free Spins feature.
Beginning with a 1x multiplier, each Reaction/win increases the win multiplier by 1. With no limit to how high the win multiplier can go, you can retrigger the feature infinitely for unlimited free spins. Bonanza has a 96% RTP rate and 26,000 x bet max wins with the exciting bonus feature the key to landing big wins. It may be simple with countless other Megaways slots copying it but Bonanza still remains the favourite.
6. Immortal Romance
Created by Microgaming (now Games Global), Immortal Romance is an iconic slot that is based on vampires. With 5 reels and 243 ways to win, it comes with a very high 96.86% RTP rate and one of the best soundtracks you’ll ever hear in a slot game.
The game is all about the iconic The Chamber of Spins. The more times you trigger it, the more free spins features you can choose from. With 4 available, there offer 5x multipliers, Vampire Bat multipliers up to 6x, Rolling Reels with an increasing multiplier up to 5x and Wine Vine symbols which give you wilds. Offering 12,150 x bet max wins, Immortal Romance is a challenge that remains as popular today as when first released in December 2011.
7. Money Train 4
Created by Relax Gaming, Money Train 4 is the last in the iconic series. Played on a 6x6 grid with Scatter Pays, you join the bandits on their last ride of the rails in a dystopian futuristic setting.
Focusing on the Money Cart Bonus feature which is a respins bonus game, Relax Gaming has added a new bandit and more special symbols which results in more explosive combinations. With 20 special symbols in total, you can win up to 150,000 x your total bet from the feature making it a bonus slot many try to conquer.
- Mobile-first Casino With Instant Withdrawals
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Jackpot Slots Bonus Features
Whilst the above slot games are the most popular bonus slots, you should also consider progressive jackpot slots. Normally randomly-triggered, jackpot features give you the chance to win a 7 or even 8-figure progressive jackpot.
Whilst the odds of winning a jackpot are extremely low, the biggest ever progressive jackpot win is an astonishing €38.4 million! The chance to win big keeps players coming back time and time again. Below are 2 of the best bonus jackpot slots in the UK:
Mega Moolah
Released by Microgaming in November 2006, Mega Moolah is an African safari-themed game with 5 reels and 25 paylines. With doubling wild wins and free spins with a multiplier up to 6x, the appeal is the Progressive Jackpot Bonus feature which is triggered randomly on any spin.
You then spin a wheel to win 1 of the 4 progressive jackpots. If you land the Mega Jackpot, you are guaranteed to win at least £2 million with an average of €6.69 million every 49 days. Due to it’s popularity, Games Global (formerly Microgaming) have a fully-fledged Mega Moolah slot series which all give you the chance to win jackpots.
- Great Slots & Exclusive Table Games
- Excellent 24/7 Customer Service
Age of the Gods
Created by Playtech, Age of the Gods is a popular choice. With a Greek mythology theme and set in Mount Olympus, this 5 reel 20 payline game comes with 4 free spins features based on ancient Greek deities.
Offering multipliers up to 5x, increasing multipliers, stacked wild reels and wild symbol transformations, you can play various features in one sitting as long as you don’t unveil Hades. You also have the added extras of 4 progressive jackpots with the Ultimate Power Jackpot awarding an average £499,000 every 44 days. In fact, all Age of the Gods series slots offer you the chance to win these jackpots.
- Bet on the Biggest Global Lotteries
- Great Live Casino
- £500k Drops and Wins Slots
Nolimit City vs Pragmatic Play Bonus Frequency
Old-school classic slots or 3-reel games are not as popular as bonus slots due to the excitement and win potential offered in the latter. Whilst we’ve outlined the most popular choices above, only 2 slot studios provide stats on the frequency of triggering the main bonus feature (which is free spins in the majority of cases).
In this section, we look at the bonus feature frequency rates from both Nolimit City and Pragmatic Play slots. First, we begin with Nolimit City:
Nolimit City Bonus Slots
Nolimit City slots are known for being extremely volatile with controversial, unique themes and graphics as well as innovative in-house mechanics and high win potential.
Whilst other slot games are ‘easier to bonus’, the challenge of triggering the main bonus feature is a feat many players find appealing. When looking at the hit frequency into the main bonus feature (i.e. free spins) for all their slot games, here is what we found:
- Highest Hit Frequency: 1 in 13 Spins into the Candle Spins feature in Blood and Shadow
- Lowest Hit Frequency: 1 in 398 Spins into the Pre-Ops or Annihilations Spins features in Disturbed
- 1 in 191 Average Hit Frequency across 99 slot games with a bonus feature
xBet Enabled!
Pragmatic Play Bonus Slots
Probably the most popular slot studios around, there are hundreds of Pragmatic Play slots to choose from. Offering a variety of mechanics, themes, bonus features and extras, below you’ll find the slot games with the highest and low hit frequency as well as the average across 380+ titles:
- Highest Hit Frequency: 1 in 20.24 Spins into the Respin feature in Star Pirates Code
- Lowest Hit Frequency: 1 in 510 Spins into the Free Spins feature in Spin & Score Megaways
- 1 in 229 Average Hit Frequency across 380+ slot games with a bonus feature
