A symbol upgrade is a feature that turns lower-paying symbols into higher-paying ones, either for a single spin or for the rest of a bonus round. A related version removes the low symbols from the reels altogether, so only the better-paying ones can land.
What symbol upgrades are
Every slot has a paytable with low-value symbols, often card ranks or simple icons, and high-value symbols. Upgrade features tip the balance towards the high end. A common design is a free spins round with a collection meter: collect enough of a special symbol and the lowest remaining symbol is upgraded, often with extra spins added at the same time.
How it works, step by step
- The feature starts, usually as part of a bonus round.
- A trigger appears. In collection designs, a meter fills as special symbols land.
- When the trigger completes, the game picks the lowest-paying remaining symbol and turns it into a higher one, or removes it from the reels.
- From then on, wherever that low symbol would have landed, the higher symbol appears instead.
- Further triggers upgrade the next lowest symbol, and so on.
- When the bonus ends, the reels return to normal.
Common variations
- Collection upgrades: the meter-based version in free spins described above.
- Low symbol removal: low symbols are taken off the reels in stages.
- Random base-game upgrades: a symbol is upgraded for one spin at random.
- Upgrade to wild: the final upgrade turns a symbol into a wild.
- Cash upgrades: in money collect and hold and win features, coin values can be upgraded to larger values or to a jackpot.
What it does to the maths and the feel
Upgrades make a bonus round progressively better the longer it goes. Early in a round the grid looks like the base game; after several upgrades it can be dominated by high-paying symbols. Rounds that reach the later upgrades pay far more than rounds that do not, which makes the bonus volatile even when it triggers at a normal rate.
The designer prices that in. The chance of reaching each upgrade level, and the value it adds, are part of the overall RTP. A game with an upgrade ladder is not more generous than one without, but its results are more spread out, which raises volatility.
As an illustration only, two runs of the same free spins round could look very different. In one, the meter fills early and the last several spins play on reels stripped of low symbols. In the other, the meter never fills and the round plays like a short run of base-game spins. Both are normal outcomes of the same feature, and neither tells you anything about the next round.
Rules in Great Britain
Symbol upgrade features are available on GB-licensed sites under the normal stake limits and game design rules. Upgrades inside a free spins round are part of the feature and cost nothing extra.
Questions people ask
When do symbol upgrades happen?
Most often during free spins, when collecting certain symbols upgrades a low symbol for the rest of the round. Some games also upgrade at random in the base game.
Is removing low symbols the same as upgrading them?
They have a similar effect: the grid is left with more of the higher-paying symbols. Removal takes the symbol out of the reel set; an upgrade turns it into another symbol.
Do upgrades carry over to the next bonus?
Usually not. Upgrades normally last for the current feature only, though a few games have persistent upgrades shown on a meter.