Certain characteristics of gambling products can increase or decrease the risk that they will cause gambling harm. The volatility of a gambling product is the variation in pay-out over time. Low-volatility games provide small but consistent pay-outs. High-volatility games provide big but rare pay-outs (e.g., jackpots). This study looked at how the volatility of online slots games affected the amount of time and money people spent. The researchers looked at the gambling behaviour of people who gambled with two UK online gambling operators. They found that people who gambled with the different operators responded differently to changes in volatility levels. This means that the link between volatility and gambling behaviour is complex. This link may also depend on other factors, such as the gambling context.