Symbol transformation slots change some of the symbols that have landed into different symbols before the win is counted: a mystery box becomes a matching icon, a character turns into a wild, or every low symbol upgrades to a higher one. The animation happens after the reels stop, but the RNG settled the final result before the spin finished.
A transformation turns landed symbols into other symbols before wins are paid.
Common forms are mystery reveals, transform-to-wild, upgrades and transform-to-cash.
The final screen is decided by the RNG at the start of the spin; the animation only shows it.
Transforming many positions at once creates rare large wins, raising volatility.
UK rules ban celebrating a 'win' that returns no more than the stake, however it's revealed.
Feature type
Symbol modifier
Also called
Mystery, morphing, switching or upgrading symbols
When it happens
After the reels land, before wins are counted
Who decides the result
The RNG, before the reels stop
Effect on volatility
Usually raises it
Fruit machine cousin
None in common use
What symbol transformation in slots means
Symbol transformation is a catch-all name for any mechanic that changes a landed symbol into a different one before the game counts wins. It's distinct from symbols that move (walking wilds) or grow (expanding symbols). Here the position stays the same; the identity changes.
Transformations turn up in the base game, in respins and especially in free spins. Our slot features hub lists them alongside related modifiers such as mystery symbols and symbol upgrades, which are specific kinds of transformation.
Five forms of symbol transformation
How symbols transform in online slots
Form
What changes
What it tends to do
Example
Mystery reveal
Blank or boxed symbols all reveal the same random symbol
Creates stacks of one symbol at once
Razor Shark's Mystery Stacks
Transform to wild
A character or marked symbol becomes a wild
Helps complete wins; often sticky
Vikings Go Berzerk Reloaded
Upgrade
Lower-paying symbols turn into higher-paying ones
Raises the value of later spins
Eye of Horus free spins
Triggered transformation
A special symbol converts every copy of another symbol
Big screen-wide changes
Curse of the Werewolf Megaways
Transform to cash or collector
Symbols turn into prize-carrying coins
Feeds a collect or respin feature
Many hold-and-win games
How a symbol transformation is decided: RNG first, animation second
It's natural to watch a mystery box flip and feel the outcome is being decided right then. It isn't. In a certified online slot the sequence runs like this:
You press spin and the stake is taken.
The random number generator produces the numbers for the whole game cycle, including where the reels stop and what any transformation reveals.
The server or game client works out the final screen and the total win.
The reels land showing the 'before' state, such as mystery boxes or untransformed characters.
The transformation animation plays to reveal the 'after' state.
Wins are highlighted and added to your balance.
The order matters for the myths below: nothing during the animation can change the result. The UK minimum of 2.5 seconds per spin covers this whole game cycle.
Worked example: a transformation on a 243-ways slot
Ways-to-win games show why transformations can be so powerful. On a 243-ways slot a win's number of ways equals the count of the symbol on each reel multiplied together. The paytable below is invented: the dragon symbol pays 20p per way for three of a kind, 50p for four and £2 for five, at a £1 stake.
Dragons on each reel, before and after every 'J' turns into a dragon (illustrative)
Reel 1
Reel 2
Reel 3
Reel 4
Reel 5
Ways and pay
Before
1
0
1
1
0
No win: reel 2 is empty
After
2
1
2
1
0
2 × 1 × 2 × 1 = 4 ways of four = £2.00
If reel 5 also had one J
2
1
2
1
1
4 ways of five = £8.00
Turning one symbol type into another changed a losing screen into a £2 win, and a single extra converted symbol on reel 5 would have quadrupled it. Because the number of ways multiplies, transformations that hit several reels at once account for many of the biggest results on ways games.
Transformations vs mystery symbols vs upgrades
The three terms overlap, and players use them loosely. A mystery symbol is a placeholder that reveals one randomly chosen symbol; every mystery on screen usually reveals the same one. An upgrade permanently changes a lower symbol into a higher one for the rest of a feature. A transformation, in the narrower sense, converts symbols that are already showing, often triggered by another symbol landing. All three move value into rare, screen-wide events, and all three are covered by the game's published RTP.
Symbol transformation slots you may know
Figures are from our slot facts. Operators can offer lower RTP versions; the help screen shows which one you're playing.
A transformation either does nothing much (two mystery boxes reveal a low symbol) or something dramatic (a full stack of mysteries reveals the top symbol across four reels). That all-or-nothing pattern is the signature of high volatility. Games pay for the dramatic outcomes with leaner ordinary spins. Transform-to-wild features that stick for a whole round, as in Vikings Go Berzerk Reloaded, also stack value into the later part of a bonus.
Symbol transformation slots: max win at UK stake limits
Players aged 25 and over can stake up to £5 a spin online and those aged 18–24 up to £2, as GOV.UK's stake limit announcement (opens in a new tab) explains. The table turns published maximums into pounds. These are ceilings almost no session reaches.
Published max win in pounds
Slot (max win)
£0.10
£1
£2
£5
Reactoonz (4,570×)
£457
£4,570
£9,140
£22,850
Mystery Reels (5,000×)
£500
£5,000
£10,000
£25,000
Vikings Go Berzerk Reloaded (25,000×)
£2,500
£25,000
£50,000
£125,000
Razor Returns (100,000×)
£10,000
£100,000
£200,000
£500,000
Play'n GO's Reactoonz is included because several of its random features change symbols on its cluster grid. Average cost works the same way as for any slot: at 96% RTP, 100 spins at 50p is £50 staked and £2 lost on average over the long run.
Symbol transformation myths
'The mystery symbols are decided as they flip.' The reveal was fixed when the spin began.
'If I'd stopped the reels, the boxes would have shown something else.' UK slots have no slam-stop, and stopping early never changes an online result.
'Lots of mystery boxes with no win means a big reveal is due.' Every spin is independent; nothing is due.
'Transformations are added to make you lose.' They're part of how the game pays its RTP; they don't change the long-run return.
Symbol transformation on fruit machines and land-based slots
Traditional UK fruit machines use physical or video reels with holds, nudges and feature boards rather than symbols that change identity. Video-reel content on Category B3 machines in bookmakers, bingo halls and adult gaming centres is closer to online games and can include mystery or transforming symbols. Those machines are capped at £2 a play and a £500 prize, pub Category C machines at £1 and £100, and all are 18+. See our online vs land-based comparison.
UK rules that apply to transforming symbols
Since 31 October 2021, online slots in Great Britain have had no autoplay, no turbo or slam-stop, at least 2.5 seconds per spin, and no celebration of a return equal to or smaller than the stake. That last rule applies however the result is revealed: a mystery reveal that pays back 30p on a 50p stake shouldn't be dressed up as a win. The losses disguised as wins rule page has the detail. UK versions of these games don't offer a bonus buy.
Where to play symbol transformation slots in the UK
Our partners' welcome offers aren't linked to a particular transforming-symbol game, and lobbies change, so search by game name. All three are for new customers aged 18+, and terms apply.
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Coral and Ladbrokes are both run by LC International Limited (Entain), so the terms may stop you holding new accounts at both. Use deposit limits and reality checks, and see our responsible gambling page for support.
Coral and Ladbrokes are both run by LC International Limited (Entain). If you already hold an account with one Entain brand, you may not be able to open a new account with another; check the terms before signing up.
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18+. Gambling should be entertainment that costs money, not a way to make it. Decide a budget before you play: plan a slot budget. Free, confidential help: National Gambling Helpline 0808 8020 133.
Frequently asked questions
What is symbol transformation in slots?
Symbol transformation is any feature that changes symbols that have already landed into different symbols before wins are counted. Examples include mystery boxes revealing a matching icon, characters turning into wilds, and low symbols upgrading to higher ones. The position stays the same; only the symbol changes. The final result is set by the RNG before the animation plays. Our mystery symbols page covers one common form.
Is the mystery symbol decided when it flips?
No. In a certified online slot, the RNG decides the whole outcome of the spin, including what every mystery symbol will reveal, at the moment the spin starts. The flip is an animation that shows a result already fixed. Nothing you do during the animation, and nothing about timing, can change it. Our page on how slot machines decide who wins explains the process.
What is the difference between symbol upgrades and transformations?
An upgrade is one type of transformation: it permanently changes a lower-paying symbol into a higher-paying one, usually for the rest of a free spins round. Transformation is the broader term, covering mystery reveals, symbols that become wild and screen-wide conversions triggered by a special symbol. All of them shift value into rarer, bigger events. Read our symbol upgrades page for that specific mechanic.
Which slots have symbols that transform?
Examples include Curse of the Werewolf Megaways, where a Golden Werewolf transforms Red Wolf symbols in free spins; Vikings Go Berzerk Reloaded, whose Berzerk Vikings turn into sticky wilds; Razor Shark and Razor Returns, with mystery stacks; Red Tiger's Mystery Reels; and Eye of Horus, where Horus wilds upgrade symbols in free spins. Game availability varies by casino. See our Razor Shark page for one example.
Why do transformations matter so much on ways slots?
On ways-to-win slots the number of ways is the count of a symbol on each reel multiplied together, so adding even one matching symbol to a reel can multiply a win. A transformation that changes several symbols across different reels at once can turn a losing screen into a big win. That's why these features are popular on 243-ways and Megaways games. Our guide to ways-to-win slot machines explains the counting.
Do symbol transformations make a slot more volatile?
Usually, yes. A transformation tends to either do very little or change a large part of the screen at once. That all-or-nothing pattern means long stretches of small results and occasional big ones, which is high volatility. The RTP is not changed by the feature; it is already part of the published figure. Our volatility explainer shows how to match volatility to a budget.
Can a transformation be celebrated if I didn't win more than my stake?
Not on UK online slots. Since 31 October 2021 games must not celebrate a return that is equal to or smaller than the stake, whether the money comes from a normal win or a dramatic reveal. Your net position and balance must also be visible. If you see a big animation for a small return, check the win against your stake. Our page on the losses disguised as wins rule explains the rule.
Do fruit machines have transforming symbols?
Traditional pub fruit machines don't usually transform symbols; their features centre on holds, nudges and feature boards. Video-reel games on Category B3 machines, found in bookmakers, bingo halls and adult gaming centres, can include mystery or transforming symbols much like online slots. B3 machines are capped at £2 a play and £500 prizes, pub machines at £1 and £100, and all are for over-18s. See slots vs fruit machines.
How much can a transforming symbol slot pay at the UK stake limits?
The most any spin or bonus can pay is the slot's published max win multiplied by your stake, with stakes capped at £5 per spin for players aged 25 and over and £2 for 18 to 24-year-olds. Vikings Go Berzerk Reloaded's 25,000× maximum, for example, is £125,000 at £5 and £50,000 at £2. Very few rounds approach these figures. Our max win glossary entry explains the term.
How can I see what a slot's transformation does before playing?
Open the game's help or paytable screen and find the feature section: it should explain what triggers the transformation, which symbols can change and into what, and whether the change lasts. You can also try the game's free demo, which in Great Britain is only available after age verification. The demo uses the same maths but can't predict real results. Our guide to the game help screen shows where to look.
Gambling can be addictive. Free, confidential help is available 24 hours a day from the National Gambling Helpline on 0808 8020 133. Visit GamCare.org.uk and GamCare, or block yourself from all UK-licensed gambling sites with GAMSTOP.
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