Slot glossary

The terms you'll meet on this site and on slot info screens, in plain language. Each links to a guide or tool where there's more to say.

RTP (return to player): The share of all money wagered on a game or mode that it pays back over the long run. A 96% RTP returns $96 for every $100 wagered on average, across millions of rounds. More on RTP.
House edge: The other side of RTP: 100% minus RTP. A 96% RTP game has a 4% house edge, which is the average cost of each bet.
Expected cost: What a round or session costs on average over the long run: amount wagered × (1 − RTP). Real results vary around it.
Volatility: How spread out a game's results are. Low-volatility games pay small amounts often; high-volatility games go quiet for long stretches and pay rarely but large. More on volatility.
Standard deviation: The statistic behind volatility: how far a single round's result typically lands from the average. This site ranks Engine slots by base-mode standard deviation.
Max win: The largest payout a game can make on one round, as a multiple of the base bet. Many games cap it, so the top outcome is exactly this amount.
Max win odds: How often a single round hits the max win, written as 1 in N. Derived from the game's published outcome table. More on max-win odds.
Hit rate: How often a round pays anything at all. A round that pays back less than its cost still counts as a hit, so hit rate says little about whether you're up.
Base bet: The stake for one standard spin. Costs of other modes, max wins and multipliers are all quoted as multiples of it.
Mode: One way to play a game: base spins, a boosted spin or a bonus buy. On Engine each mode has its own cost, RTP and outcome table.
Bonus buy: A mode that pays a fixed price, usually 20× to several hundred times the bet, to start the bonus feature straight away. Its RTP can differ from the base game. More on bonus buys.
Boosted spin (ante bet): A spin that costs more than the base bet, typically 1.25× to 10×, in exchange for better odds of triggering the feature.
Feature / free spins: The bonus round of a slot, usually free spins with extras like multipliers or sticky symbols. It's where most of a slot's large payouts come from.
Multiplier: A factor that multiplies a win, such as a 10× multiplier turning a 2× win into 20×.
Break-even multiplier: In a bonus hunt, the average win as a multiple of the bet that the bonuses need to pay for the hunt to finish level. Bonus hunt calculator.
Bonus hunt: Collecting or buying a batch of bonus features first and opening them all afterwards, tracking whether their total pays back their total cost.
Wagering requirement: The total amount a casino bonus must be bet before it can be withdrawn, written as a multiple of the bonus. Wagering calculator.
Provably fair: A way of generating results that lets players check afterwards that a round wasn't changed, using a server seed, a client seed and a nonce. More on provably fair.
Server seed, client seed and nonce: The three inputs to a provably fair result. The casino commits to a hashed server seed, the player sets a client seed, and the nonce counts rounds. How to verify a result.
Outcome table: The full list of results a mode can produce and their weights. On Engine these tables are public, which is what makes exact RTP and odds possible.
Math version: An Engine game's published maths are versioned. A studio can release a new version with different odds or RTP; older versions stay public.
RTP cut: When a newer math version of a game has a lower RTP than an earlier one. The RTP checker lists games where this happened.
Stake Engine (Engine): The platform where independent studios publish slots with fully public maths. What Stake Engine is.
Turnover: The total amount wagered on a game in a period. This site uses 30-day real-money turnover from Engine Insights to rank popularity.
Session: One continuous stretch of play. Over a session, results are dominated by volatility; RTP only shows through over a very large number of rounds.

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