The Truth About RNG and Fairness in Online Casinos
RNG is what online casinos use to determine the outcome of a game: which card comes next, which symbols land on the reels, where the ball lands on the roulette wheel. In this article, you will discover what the RNG is, how independent labs test the RNG, how RTP and variance come into play, and how to verify whether a casino is honest. We will debunk popular misconceptions and provide actionable tips that you can apply today.
What Is RNG in Online Casinos?
RNG means random number generator. It is a system that makes numbers that no one can guess. Each new number does not depend on the last one. In casino games, the number maps to a game event. That number can mean which card comes next, where a roulette ball stops, or where a slot reel lands.
Pseudo-RNG vs True RNG
Most online games use a pseudo-RNG (PRNG). A PRNG is a math program. It takes a “seed” and makes a long stream of numbers that look random. It is very fast and works well for games. A true RNG (TRNG) uses real-world noise, like tiny changes in hardware. TRNGs are common in some security tools. For casino games, PRNG is standard. It is fine when done right and tested by labs. You can read a simple intro on NIST’s randomness tests here: NIST SP 800-22.
Seeding, Entropy, and Mapping Outcomes
The seed is a start value. Good systems use high-quality “entropy” (unpredictable bits) to make the seed. The PRNG then makes a stream of numbers. The game maps those numbers to outcomes. For a slot, the number maps to reel stops. For roulette, it maps to 0–36. For cards, it maps to a shuffle and deal order. The mapping is fixed and must not bias any outcome.
How Independent Labs Test and Certify RNGs
Independent test labs check RNGs. They also test game math and game mapping. These labs run many checks. They also audit updates over time. Look for logos and certificates from trusted labs and confirm them on the lab’s site.
Who Audits
- eCOGRA (approved testing and ADR in many markets)
- Gaming Laboratories International (GLI) (global standards like GLI-11 and GLI-19)
- iTech Labs (RNG and game certifications)
- BMM Testlabs (RNG, game, and system audits)
Check for lab logos and certificates and verify them with the lab.
What Tests Look Like
Labs check the PRNG code and the seed process. They test the output with tools like NIST SP 800-22 and academic suites like TestU01. They check for bias and patterns. They also test the mapping from RNG numbers to game outcomes. This is key. Even a good RNG can be used in a bad way if mapping is not fair. Labs also review change logs and version control. They check builds that go live. They repeat tests after big updates.
Ongoing Compliance and Change Control
Many rules need continued checks, not just one test. For example, the UK Gambling Commission has Remote Technical Standards (RTS) that cover software change control, testing, and reporting. GLI also publishes standards for online systems, like GLI-19 for interactive gaming. Reputable casinos and game studios follow these rules and get re-tests when needed.
RNG Fairness vs RTP, Volatility, and House Edge
RNG is about random picks. RTP, volatility, and house edge are about math over time. Many players mix these up. Let’s split them clearly.
RNG Ensures Unpredictability; RTP Is Long-Term
RNG makes each spin or hand random. RTP means Return to Player. If a slot has 96% RTP, it pays back 96% of all bets in the very long run. This is not a promise for your session. It is a long-term average over many millions of spins. The RNG and the RTP work together: the RNG picks outcomes; the game math sets how often each outcome appears over time.
Volatility and Short-Term Swings
People get those confused all the time.
Why “Hot” and “Cold” Machines Are a Myth
Many people think a machine gets “hot” or “cold.” This is a myth. A fair RNG has no memory. Each spin is new. Past spins do not change future spins. Time of day, day of week, and your last win do not matter to a tested RNG.
Are Online Casinos Able to “Flip a Switch”? Myths vs Facts
Some fear that casinos can press a button to make you lose. In licensed markets, this is not allowed and is very risky for them. Here are the facts:
- Game code comes from the game provider, not the casino. It is tested by labs. Changing it would break rules.
- Regulators like the UK Gambling Commission (UKGC), the Malta Gaming Authority (MGA), and U.S. state bodies like the New Jersey DGE enforce strict checks. Violations can mean big fines or loss of license.
- “Account-based odds” for slots are not allowed in these markets. Odds come from the game math, not from who you are.
- Demo vs real money: in licensed markets, the math and RNG must match. Only the stake type changes. Check your regulator’s rules to confirm.
How to Verify a Casino’s Fairness Yourself (Simple Checklist)
Low variance is about frequent small wins.
1) Check the License
- Find the license number in the site footer.
- Confirm it on the regulator site: UKGC Public Register MGA Licensee Register New Jersey DGE Ontario AGCO/iGaming Ontario
- UKGC Public Register
- MGA Licensee Register
- New Jersey DGE
- Ontario AGCO/iGaming Ontario
- UKGC Public Register
- MGA Licensee Register
- New Jersey DGE
- Ontario AGCO/iGaming Ontario
2) Confirm Lab Certificates
- Look for lab logos. Click them. The link should go to a page on the lab site, not only a picture.
- Check the date, scope, and products. You should see RNG or game certifications on eCOGRA, iTech Labs certificates, GLI, or BMM.
3) Review RTP by Game and Jurisdiction
- Good sites and providers publish RTP by title. Some markets let operators pick among approved RTP versions. This must be disclosed.
- In the UK, see the RTS guidance on information for players, including RTP display.
4) Scan Terms, Payments, and Complaints
- Withdrawal rules should be clear. Payout times should be stated.
- Bonus terms should be fair. Watch for very high wagering or clauses that void wins for small mistakes.
- Check complaint history. Look for a working ADR (alternative dispute resolution). In the UK, see UKGC advice on complaints and ADR.
5) Want Vetted Options?
This checklist is to be used prior to playing. It will take you a few minutes and can save you trouble.
“Provably Fair” in Crypto Casinos — How It Works
Some crypto casinos use a “provably fair” system. The idea is simple: the site shows a hash (a one-way code) of a server seed before your bet. You bring your client seed. There is also a nonce (a counter). After the bet, the site reveals the server seed. You can hash it and see it matches the pre-bet hash. Then you can re-create the roll from the seeds and nonce. If your re-roll matches, the result was not changed after the fact.
This uses hash functions. You can learn what a cryptographic hash is here: Cloudflare: What is a cryptographic hash function?
Limits to know: “Provably fair” proves the random input was not altered after commit. It does not set RTP or remove the house edge. It also does not prove the site is licensed or pays on time. You still need basic checks: license, audits, and payment ethics.
Live Dealer Games and Fairness
Live casino games use real cards and wheels. Studios use cameras, trained dealers, and logs. Some live games use continuous shufflers. Others use manual shuffles. Labs and regulators also check live systems and procedures. Rules for remote gaming tech, like the UKGC’s RTS, cover this space. GLI also tests live dealer setups under GLI standards. As with RNG games, the house edge is in the rules, not in dealer behavior.
Red Flags That Suggest Unfair Play
- No clear license number. Or the license does not match the brand on the regulator site.
- Fake or dead lab “seals.” Logos that do not link to a valid lab page.
- Hidden or altered RTP with no notice. Or RTP that differs from the provider page without a reason.
- Unclear or predatory terms. For example, vague “irregular play” rules, or bonuses that void wins for tiny errors.
- Many unresolved complaints and no ADR path.
- Pushy sales tactics. Claims like “guaranteed wins” or “beating the RNG.” These are false.
Responsible Gambling and Legal Notes
Check if online gambling is legal in your country or state. Play only on licensed sites. Set deposit and loss limits. Take breaks. Never chase losses. If you need help, reach out:
- BeGambleAware (UK)
- GamCare (UK)
- National Council on Problem Gambling (US)
This is only a tool, you should always verify the information.
FAQs
Is RNG truly random?
It relies on cryptographic hash functions: Cloudflare: What is a cryptographic hash function?
Can casinos rig RNGs?
In licensed markets, this would break the law and lab rules. Game code comes from providers and is tested by labs like GLI, eCOGRA, iTech Labs, or BMM. Regulators like the UKGC, MGA, and the New Jersey DGE watch for abuse. Bad actors face fines and bans.
Are demo and real-money games identical?
In many licensed markets, yes. The RNG and math must match. Only stakes and some features (like jackpots) may differ. Check your local rules. The UKGC’s RTS explains this for the UK.
Do casinos change RTP by country?
Sometimes, yes. Some providers ship several RTP versions. The operator must use only approved versions and must disclose RTP. Always check the help screen for each game and your regulator’s rules.
Are live dealer games fair?
Only play on regulated platforms.
What is a good RTP?
Take breaks.
How do I check a lab certificate?
If you need further guidance, please contact:
What does “provably fair” prove?
Disclosure: If an affiliate link or an ad exists on a site, it should be noted. A good site should have an editorial policy and an updates policy. Check for a contact us section and a privacy policy.
Bottom Line
A fair online casino runs on a tested RNG, clear RTP, and strict rules. Labs check the code, the math, and the mapping. Regulators enforce updates and change control. Myths like “hot slots” or “switched odds” do not hold up under these systems. Use the simple checklist: verify the license, confirm lab seals, read RTP and terms, and scan complaints. If you want a head start, use a trusted review hub, then double-check on regulator and lab sites before you play. Stay safe, play for fun, and set limits.
Smartphones Casinos
