Autoplay Caps at 25 Spins Cut Slot Sessions 16%
A mandatory 25-spin ceiling on autoplay reduced average slot session length by 16% among players who used the feature, according to a 14-month study of 4.2 million sessions across three licensed European markets. The drop was measured in time-on-machine, not spin count: players still spun roughly as often, but they stopped sooner after autoplay halted. The finding lands as U.S. regulators weigh whether to impose similar caps on the seven states that currently permit autoplay in some form.
What the Study Actually Measured
The research, published in March by a gambling-studies unit at a European university and shared with regulators in two jurisdictions, tracked 4.2 million slot sessions between January 2023 and February 2024. Roughly 890,000 of those sessions involved autoplay at least once.
The design matters. Autoplay, for readers who play mostly in U.S. markets where it's restricted, lets a player preset a number of spins — 10, 50, 100, sometimes 1,000 — and walk away from the button. The reels keep turning until the count runs out or a stop condition triggers. It's standard on most offshore sites and on regulated platforms in the UK, Malta, Sweden, and several other markets. In the U.S., it's a state-by-state patchwork: New Jersey, Pennsylvania, Michigan, and a handful of others have either banned it outright or left it to operator discretion, while some tribal and social casinos still offer it.
The study split its sample into three groups:
- Control markets where autoplay limits stayed at the pre-study level (typically 100 spins per activation)
- Capped markets where regulators imposed a hard 25-spin ceiling
- A third cohort where operators voluntarily lowered caps to 50 spins
Only the 25-spin group showed a statistically significant change in session length. The 50-spin cohort moved less than 3%, which the authors flagged as within noise.
Session length in the capped markets fell from a mean of 38.4 minutes to 32.3 minutes — a 15.9% decline, rounded to 16% in the paper's abstract. Spin count per session dropped only 4.1%. That gap is the interesting part. Players didn't spin less per minute; they simply left earlier.
Why the Gap Between Time and Spins Matters
If a cap only reduced the total number of spins, you could argue it just interrupted play and players resumed elsewhere. The data doesn't support that. Because spin frequency held roughly steady, the reduction came from players ending sessions rather than slowing down within them.
The authors offer two explanations, neither fully proven. The first is friction: each time autoplay stops at 25, the player has to make a conscious decision to restart it. Some don't. The second is that a 25-spin block is short enough that players treat it as a discrete unit of play — one "round" — rather than an open-ended session. When the round ends, they're more likely to check their balance.
That second explanation lines up with earlier behavioral research on slot design, which found that players mentally segment sessions around feature triggers, bonus rounds, and other natural break points. A 25-spin cap manufactures a break point every few minutes.
The Regulatory Landscape in the U.S.
Autoplay is not a federal issue. The Wire Act, the Unlawful Internet Gambling Enforcement Act, and the various state compacts that govern online casino and poker say nothing about spin automation. It falls to state gaming regulators, and they've split.
New Jersey allows autoplay but requires operators to offer a stop-loss and a single-session loss limit. The Division of Gaming Enforcement has not imposed a spin cap. Pennsylvania permits autoplay with mandatory session reminders every 60 minutes. Michigan allows it with no cap but requires a "reality check" pop-up at intervals the player sets, defaulting to 60 minutes. Connecticut and West Virginia have taken similar approaches. Nevada, which regulates online poker but not online slots, has no position because the product doesn't exist there.
The patchwork means a player in Philadelphia and a player in Newark can have materially different autoplay experiences on the same brand's platform, depending on which skin they're using.
The study's authors were careful not to recommend a specific policy. But the 16% figure has already been cited in at least one state's responsible-gambling advisory committee meeting, according to minutes published in February. Expect it to surface again as more states legalize iCasino — and as the ones that already have it revisit their technical standards.
The Industry Pushback
Operators have a predictable objection, and it's not baseless. Capping autoplay at 25 spins increases the number of times a player must re-engage with the interface. For high-volume players — the ones who generate a disproportionate share of revenue — that's friction that pushes them toward unregulated offshore sites where no cap exists.
One European operator that participated in the study, speaking on background, said its 25-spin cohort showed a small but measurable uptick in players closing accounts and reopening on .com sites. The study's authors acknowledge this but note that self-exclusion and deposit-limit usage also rose in the capped markets, which they interpret as a sign that some at-risk players were engaging with safer tools rather than leaving altogether.
The counterargument: if a player leaves a regulated site because of a 25-spin cap, that's a policy failure, not a policy success. And offshore sites offer no deposit limits, no reality checks, and no route to a state self-exclusion list.
What the Numbers Don't Show
A 16% reduction in session length is a headline figure, but it's an average across a heterogeneous population. The study's own breakdown shows the effect was concentrated.
Among players the authors classified as "low-intensity" — fewer than 200 spins per week — the session-length drop was 22%. Among "high-intensity" players — more than 1,000 spins per week — it was 6%. That's a meaningful difference. The cap appears to work best on the players least likely to develop problems, and least well on the ones most likely to.
That's not an argument against the cap. A 6% reduction in session length among heavy players is still a reduction, and heavy players are the group most exposed to harm. But it does complicate the simple story that a spin cap is a broad-spectrum harm-reduction tool.
The study also didn't measure whether players who shortened sessions compensated by playing on more days, or by increasing stake size within shorter sessions. Both are plausible. Both are testable. Neither was tested.
There's also the question of what "session" means. The study defined a session as continuous play with no gap longer than 30 minutes. If a player stops for 31 minutes and resumes, that's two sessions. A cap that encourages more frequent short breaks would inflate session counts while reducing average length — which is arguably the intended effect, but it makes the 16% figure harder to interpret as a pure measure of reduced play.
The 25-Spin Number Itself
Why 25? The study didn't test other caps, so the paper can't say whether 20 spins would work better or 30 would work nearly as well with less friction. The 25 figure appears to have been chosen by regulators in the capped markets, not derived from the data. The authors note this as a limitation.
A separate 2022 study in a single market tested caps of 10, 25, and 100 spins and found that 10-spin caps reduced session length by 31% but produced a sharp increase in manual spin rates — players simply held the button down themselves. The 25-spin cap produced a smaller session reduction but no compensating manual-spin increase. That's a point in favor of 25 as a middle ground, though the 2022 study had a smaller sample and wasn't replicated.
The Practical Question for U.S. Regulators
If a state wanted to adopt a 25-spin cap tomorrow, it could. The technical standard is trivial to implement; every major platform already supports configurable autoplay limits because they're required in multiple European jurisdictions. The question is whether the evidence justifies it.
The case for: a 16% reduction in average session length, concentrated among moderate players, with no evidence of a compensating increase in manual spin rate, and with a corresponding rise in deposit-limit and self-exclusion usage in the capped markets.
The case against: the effect is small among the heaviest players, the mechanism is poorly understood, the 25-spin figure is arbitrary, and there's at least anecdotal evidence of migration to unregulated sites.
Both cases are reasonable. What's not reasonable is treating the 16% figure as a settled fact. It's one study, in three markets, over 14 months, with a definition of "session" that flatters the result. It's the best data available on the question, and it's better than nothing. But it's not the last word.
The more interesting question is what happens next. If a U.S. state adopts a cap and the session-length reduction replicates, that's a strong signal. If it doesn't — if American players behave differently, or if the offshore migration is larger here because the legal market is younger and less sticky — then the 16% figure becomes a European curiosity rather than a template.
The study's authors are already recruiting for a follow-up that would track a U.S. cohort if a state volunteers. As of this writing, none has.