The house edge: the only number that matters long-term
Every casino game is designed so that, over a sufficiently large number of rounds, the operator retains a fixed percentage of all money wagered. This is the house edge — and it is the price you pay for entertainment.
It is not a trap or a cheat. It is disclosed mathematics, built into the rules of the game itself. A European roulette wheel has one zero pocket; that single pocket is the entire source of the house edge on that table.
House edge by game type
| Game | Typical house edge | Notes |
|---|---|---|
| European Roulette | ~2.7% | One zero; avoid American (5.26%) |
| French Roulette (La Partage) | ~1.35% | Even-money bets only |
| Blackjack (basic strategy) | 0.5–1% | Strategy-dependent |
| Baccarat (Banker bet) | ~1.06% | Tie bet is 14%+ — avoid |
| Video Poker (full-pay) | 0.5–1% | Requires correct strategy |
| Slots | 2–10%+ | Varies by game and provider |
| Keno | 20–35% | Extremely high edge |
Playing a game with a lower house edge doesn’t guarantee winning — variance is high in the short run — but it stretches every dollar of your budget further over time. Combine this with the bankroll management principles to keep sessions sustainable.
What is an RNG?
A Random Number Generator is software that produces sequences of numbers at thousands of outputs per second. In a slot, each spin queries the RNG at the exact millisecond you press the button, mapping the result to a reel combination. In card games, the RNG shuffles a virtual deck.
There are two types:
- PRNG (Pseudo-RNG): Algorithm-based, seeded by a non-predictable input. Used in most online slots and table games.
- TRNG (True RNG): Uses physical entropy (electrical noise, etc.). Less common; mainly used in high-stakes applications.
For practical purposes, a certified PRNG is statistically indistinguishable from true randomness across the bet counts any player will ever make.
Independent certification
RNG integrity is verified by third-party testing labs that audit:
- Statistical distribution of outcomes over millions of rounds
- Seed unpredictability
- That the live game software matches the tested build
Labs to recognise: eCOGRA, BMM Testlabs, iTech Labs, GLI. Their certification marks appear in casino footers. No certification = no independent verification of fairness.
The “due” fallacy
A common misconception is that a slot is “due” for a win after a long losing streak. This is false. Each spin is independent — the RNG has no memory of previous outcomes. A machine that has not paid out in 1,000 spins has exactly the same odds on spin 1,001 as it did on spin 1.
Check which operators publish verified RTP figures and hold credible licences in our casino reviews. For context on how licences enforce RNG auditing requirements, see our licensing guide.