Symbol upgrades in slots

What symbol upgrades in slots actually are

An upgrade is any rule that replaces part of the game state with a richer version of itself. In the narrowest sense, it means a low-paying symbol such as a 10 or J being turned into a higher payer, such as a king or a premium character. Developers also use the word for multiplier steps (2× becoming 3×) and for bonus rounds that move up a tier, so the label on a game’s help screen can mean any of the three.

What all three share is direction: something is only ever improved, never downgraded, and the improvement normally sticks for the rest of a bonus round. That persistence is why upgrades sit mostly in free spins, where the game has a defined start and end. A base-game upgrade, if a slot has one, tends to last for a single spin.

Upgrades belong to the wider family of slot machine features, alongside wilds, multipliers and respins. They are not a separate type of slot; any five-reel video slot, Megaways game or grid slot can include them.

How a symbol upgrade feature works, step by step

Under the artwork, an upgrade is a lookup change. The random number generator picks the reel stops, and the game then applies its rules to the symbols that landed. A typical upgrade sequence runs like this:

1. You press spin; the RNG picks a stop on each reel strip before any animation starts.
2. The game checks whether an upgrade condition has been met: a collect symbol, a full meter, a set number of special icons or a random trigger.
3. If it has, the game rewrites the affected symbol IDs, either on the visible grid only or on the reel strips used for later spins.
4. Wins are then evaluated against the paytable using the upgraded symbols.
5. If the upgrade is persistent, the new state is stored and carried into the next spin of the feature.
6. When the feature ends, the reels go back to their normal strips and the meter resets.

The important detail is step 3. A grid-only upgrade improves the spin you are looking at. A reel-strip upgrade changes every later spin in the feature, because the weaker symbol simply stops existing on the strips. The second kind is where the big swings come from.

Three kinds of upgrade you will meet in online slots

Reading the help screen gets easier once you know which family a game’s upgrade belongs to. The table below groups them by what actually changes.

A game can stack several of these. A free-spins round might upgrade its wild collector, then move to a higher bonus tier, then add a multiplier step, each driven by a separate counter.

Worked example: what an upgrade does to a win

Take an illustrative 5-reel, 10-line slot at a £1 total stake, so each line costs 10p. The paytable below is invented for the example, not taken from any real game, but the shape matches most video slots: the card royals pay little and the premiums pay more.

Suppose free spins start with all four symbol types on the strips and an upgrade meter that turns every 10 into a K once filled. Before the upgrade, three 10s on two lines pay 2 × 50p = £1. After it, the same landing pays 2 × £1 = £2, and any spin that would have shown 10s now shows Ks. If a later step turns K into the premium, a five-symbol line jumps from £2.50 to £20.

Multiplier ladders: the upgrade in Big Bass slots

The best-known upgrade in UK lobbies is the collect ladder in Big Bass Bonanza. During free spins, the Fisherman wild collects the cash values on fish symbols. Every fourth Fisherman collected adds 10 more spins and moves the collection multiplier up, first to 2×, then 3×, then 10×. The slot is listed at 96.71% RTP, high volatility, with a 2,100× max win.

Later games in the series reworked the idea. Our spec sheet for Big Bass Keeping It Reel lists free spins in which Fisherman wilds collect fish prizes and upgrade multipliers, with a 10,000× max win; OLBG’s listing for Keeping It Reel (opens in a new tab) sets out the same structure. The more steps on the ladder, the more of the slot’s return is held back for players who reach the top.

That is the real cost of an upgrade ladder: the base game and the early steps pay less so that the later steps can pay more. Our page on progressive multipliers covers the multiplier side in more detail.

Bonus tier upgrades in Nolimit City and Relax slots

Some studios upgrade the whole free-spins round. Instead of better symbols, you move to a better version of the bonus, with more wilds, larger multipliers or extra reels.

All four list lower-RTP versions too, so the figure at your casino may differ. Kenneth Must Die and The Rave come from Nolimit City, a studio whose games are built for very wide swings. Money Train 5 and Fist of Destruction follow the same idea from different studios.

Symbol upgrades, RTP and volatility

An upgrade does not add money to a slot. The developer builds the whole game, upgrades included, to a target RTP, so value given to upgraded spins is value taken from somewhere else, usually small base-game wins. The result is a lumpier distribution: more empty spins and a fatter tail of large results. In other words, upgrades push volatility up.

Here is what that means in money. At 96.04% RTP, 100 spins at 20p is £20 staked, with a long-run average cost of about 79p. Any single session can land far from that average in either direction.

A max win is a ceiling written into the game rules, not a target. The vast majority of upgraded bonus rounds finish far below it, and many end below the stake that triggered them.

Upgrades versus transformations and mystery symbols

Three features look alike on screen but follow different rules. An upgrade only moves a symbol up the paytable. A symbol transformation can turn symbols into anything the rules allow, including a random symbol of equal value. Mystery symbols all reveal the same randomly chosen symbol after they land.

El Paso Gunfight shows the difference well. According to Slotcatalog’s El Paso Gunfight listing (opens in a new tab), its Deputy badge turns every low-value symbol into one randomly chosen low-value symbol. That merges symbols rather than upgrading them: the result can be a 10 just as easily as an A, but every low position now matches, which builds wins across the grid.

The fruit machine version of an upgrade

UK pub fruit machines have used upgrade logic for decades, just without the word. A feature trail lets you climb a board of cash and feature positions, and a cash ladder steps a prize up rung by rung, often with an option to gamble the current rung on the gamble ladder.

The limits differ from online play. A Category C pub machine has a £1 maximum stake and a £100 top prize under the Gambling Commission’s gaming machine categories (opens in a new tab), so no amount of climbing can exceed £100 in a single game. These machines are 18+ only.

Myths about upgrade meters and full collections

• Myth: a meter that is nearly full means the slot is about to pay. Fact: each spin is settled independently; a nearly full meter only means one more qualifying symbol will trigger the next step, and the odds of that symbol landing are the same as on any spin.
• Myth: leaving a game with a saved meter wastes value someone else will collect. Fact: online, saved progress is normally linked to your own account and stake level; the help screen says whether a meter is saved and for how long.
• Myth: upgraded symbols are more likely to land. Fact: the upgrade only changes what a symbol is worth once it lands, not how often it lands.
• Myth: an upgrade-heavy slot is ‘hot’ after a big bonus. Fact: there is no such thing as a hot or loose machine; past spins have no effect on future ones.

UK rules that shape upgrade slots

Every upgrade slot offered to players in Great Britain works within the same design rules. Since 31 October 2021 there is no autoplay, each spin must take at least 2.5 seconds, and there is no turbo or slam-stop, as set out in the Commission’s responsible product design standard (opens in a new tab). Stakes are capped at £5 a spin for players aged 25 and over and £2 for 18–24s; see our page on online slot stake limits.

Bonus buy options are not offered on slots at UK-licensed casinos, so the only way into an upgraded free-spins round is to trigger it during normal play. The game’s rules and RTP must be available in the help screen; our guide on how to find a slot’s RTP shows where to look.

Where to play slots with upgrade features in the UK

The upgrade ladder in Big Bass Bonanza is the one most UK players meet first, and it is the game PlayOJO’s new-customer offer is played on: deposit at least £10 for 80 free spins at 10p each, with no wagering on winnings. Coral’s offer gives 100 free spins at 10p on selected games after you bet £10 on slots, and Ladbrokes gives up to 500 free spins (50 a day for 10 days) after you play £10 on slots. All three are 18+ and terms apply; check eligible payment methods and expiry before you deposit.

For the other games named here, search each casino’s lobby, because game availability changes. Our casino pages list the licence and payment facts for each partner. Treat any slot as paid entertainment and set a deposit limit first; free, confidential help is available from GamCare (opens in a new tab) on 0808 8020 133.

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.