An online casino is a website or app licensed to offer casino games — slots, table games, and live dealer games — for real money. Results are decided by a certified random number generator (RNG) for most games, or by a live-streamed human dealer for live tables. There are thousands of them online, and the gap between the best and worst is huge: two sites can offer the same slot and still be completely different bets, once you factor in licensing, payout speed, and how honestly the bonus terms are written.
This guide covers the basics you need before you play anywhere — what licensing actually guarantees, how the math behind the games works, and what to check before you create an account.
What is an online casino?
An online casino is a regulated gambling operator that lets you play casino games over the internet instead of at a physical venue. Most run on software from third-party game studios, host it under a gambling license issued by a national or regional regulator, and process deposits and withdrawals through banks, cards, e-wallets, or crypto rails.
The two things that make an online casino legitimate rather than a website that just looks like one are a real gambling license and independently audited games. Neither is visible in the games themselves — you have to check for them.
How licensing and regulation work
A gambling license means a regulator has reviewed the operator's finances, game fairness, and player-protection policies, and holds the authority to fine or shut it down if it breaks the rules. Well-known regulators include the Malta Gaming Authority (MGA), the UK Gambling Commission (UKGC), and the Curaçao Gaming Authority — each with different requirements, so a license is a baseline, not a single fixed standard.
In practice, a real license gets you three things: independent testing of the RNG by a lab like eCOGRA or iTech Labs, a formal process for disputing a withheld payout, and (with stricter regulators) a requirement that player funds be kept separate from the operator's own operating money.
Note
Every licensed operator is required to display its license number, usually in the site footer. If you can't find one — or the number doesn't match anything on the regulator's own public register — treat that as a hard stop, not a detail to overlook.
What to check before you sign up
Before creating an account anywhere, run through the same checklist:
- License and regulator — confirm it's current and verifiable on the regulator's website, not just claimed on the casino's own page.
- Game selection and providers — recognizable studios (the kind that supply multiple licensed casinos) are a decent proxy for game fairness, since those studios are independently audited themselves.
- Payment methods and withdrawal speed — deposits are almost always instant; it's withdrawal speed and any withdrawal caps that separate good operators from slow ones.
- Customer support — live chat availability and response quality matter far more than most players expect, usually only once something's gone wrong.
- Independent reviews and complaint history — a site with no complaints anywhere is rarer than a site that resolves its complaints quickly and visibly.
How casino bonuses actually work
Bonuses are a marketing cost the casino accepts in exchange for rules that make the bonus hard to withdraw in full. The rules that matter most:
- Wagering requirement — how many times you must bet the bonus (and sometimes the deposit too) before you can withdraw anything. A "20x" requirement on a $50 bonus means $1,000 in total bets before cashout.
- Maximum bet while a bonus is active — placing a single bet above this cap can void the entire bonus, even if you didn't know the limit existed.
- Game weighting — slots typically count 100% toward wagering requirements; table games often count 10% or less, since their house edge is lower.
- Maximum cashout — some bonuses cap how much you can withdraw from bonus winnings, regardless of how much you actually won.
Note
Read the bonus terms before you claim, not after you've already started playing. A bonus with a lower headline value and fair terms is worth more than a bigger one with terms designed to make it unwithdrawable.
The math behind the games: RTP and house edge
Return to player (RTP) is the percentage of all money wagered on a game that gets paid back to players over a very large number of rounds. House edge is simply what's left: 100% minus RTP.
Example
A slot with a 96% RTP has a 4% house edge. Over millions of spins across all players, for every $100 wagered on that game, $96 is paid back out in winnings and $4 is kept by the casino, on average.
The critical word there is "average" — RTP is a long-run statistical property of the game, not a prediction of what happens in your session. Short-term results are driven by variance: a high-RTP game can still lose money for a hundred spins in a row, and a low-RTP game can pay out a huge win on the very first spin. RTP tells you what to expect over thousands of rounds, not what will happen in the next ten.
Types of casino games at a glance
| Game type | How it works | Typical house edge |
|---|---|---|
| Slots | RNG-driven spins, fixed RTP set by the game | 2-10%, varies by title |
| Blackjack | Card game against the dealer, skill affects outcome | Under 1% with correct strategy |
| Roulette | Ball lands on a numbered wheel | 2.7% (European) to 5.3% (American) |
| Live dealer | Real dealer, streamed video, real cards/wheels | Similar to the equivalent table game |
| Video poker | Draw-poker machine with a fixed payout table | Under 1% to ~5%, depends on the paytable |
These are general ranges, not guarantees — the exact number always depends on the specific game and its rules, not just the category.
Playing safely
Everything above assumes you're playing within a budget you've set on purpose, not chasing losses or gambling with money you need elsewhere. If you're new to online casinos, it's worth reading our guide to gambling safely alongside this one — the two are meant to be read together, not in sequence.