Random Number Generators (RNGs) are the backbone of digital gambling. Whether it’s an online slot machine, virtual roulette, or a card shuffle in poker, the integrity of the game depends on the unpredictability of the outcome. But randomness alone isn’t enough—RNGs must also be fair, auditable, and compliant with regulations.
In this post, we’ll break down how RNGs are tested in the gambling industry, who oversees the process, and what makes an RNG “compliant” in real-world terms.
What Is an RNG in Gambling?
At its core, a Random Number Generator is a system—either hardware-based or algorithmic—that produces sequences of numbers without any discernible pattern. In online casinos, these numbers determine the outcome of spins, card deals, dice rolls, and other game mechanics.
There are two main types:
- Pseudo-Random Number Generators (PRNGs): Software-based, deterministic systems using seed values to simulate randomness.
- True Random Number Generators (TRNGs): Hardware-based systems that generate numbers using physical processes (like electrical noise) to ensure pure unpredictability.
Most online casinos use PRNGs because they’re faster, cheaper, and easier to scale. But they require rigorous testing to ensure fairness.
Why RNG Testing Matters
In a regulated environment, players must trust that each spin or deal is random, not influenced by the house or third parties. RNG testing proves that the outcomes:
- Are statistically random within acceptable margins
- Cannot be manipulated or predicted
- Match published Return-to-Player (RTP) rates over the long term
- Comply with the technical standards of the licensing jurisdiction
Without this testing, game results could be biased—or even rigged—and players would have no way of knowing.
Who Tests and Certifies RNGs?
RNG testing isn’t done in-house by the operators. It’s handled by accredited third-party labs approved by gaming regulators. Some of the most recognized labs include:
- eCOGRA
- iTech Labs
- GLI (Gaming Laboratories International)
- BMM Testlabs
These labs are licensed to verify RNG fairness and provide certification for use in licensed jurisdictions. They work with both game developers and operators to ensure compliance.
Once certified, an RNG can be deployed in games that are then also tested to verify correct integration.
How RNGs Are Tested Step by Step
The testing process is technical, standardized, and must meet regulatory criteria. Here’s how it typically works:
1. Code Review
The lab begins with a full code audit of the RNG algorithm. This ensures that:
- It uses secure mathematical formulas (e.g., Mersenne Twister, SHA-based PRNGs)
- There are no backdoors, biases, or hidden behaviors
- It operates independently of game outcomes or bet size
2. Statistical Testing
Next, large-scale simulations are run using the RNG to verify randomness. This includes:
- Chi-Square Tests: Measure frequency distribution of outcomes.
- Diehard Tests / NIST Tests: Advanced randomness tests used to detect subtle patterns.
- Serial Correlation Checks: Confirm that current outputs aren’t predictable based on previous results.
Millions of iterations are run to validate statistical uniformity and distribution.
3. Game Integration Validation
Once the RNG is tested in isolation, labs test how it integrates with actual games. They check:
- That outcomes are correctly drawn from the RNG
- That the game logic applies rules fairly based on those outcomes
- That advertised RTP values are accurate over time
This ensures that even if the RNG is fair, the game mechanics don’t introduce unintended bias.
4. Source Code Hashing and Version Locking
To prevent tampering, the certified version of the RNG code is hashed (digitally fingerprinted) and version-locked. This ensures that the live version matches what was tested.
Any future changes must be re-submitted for testing.
Compliance Across Jurisdictions
Different regulators have different technical standards. For example:
| Region | Certification Requirement | Common Labs Used |
|---|---|---|
| UK (UKGC) | RNG + RTP Testing | eCOGRA, GLI |
| Malta (MGA) | RNG Certification + Game Testing | BMM, iTech Labs |
| New Jersey (DGE) | RNG + System Evaluation | GLI, DGE In-House |
| Australia | RNG + Payout Audit | BMM, iTech Labs |
Operators must align their RNG certifications with each jurisdiction’s regulatory body. Using the wrong certification can lead to fines or license suspension.
What Players Can Look For
While players can’t test RNGs themselves, they can check for trust signals:
- Game Certification Labels: Many games display lab seals or certification info
- Licensing Information: Reputable operators use RNGs tested by approved labs
- Consistent RTPs: Published payout rates should be verifiable and match lab results
- Transparent Audit Trails: Top-tier platforms publish audit results or reports on RNG fairness
If these aren’t visible or seem vague, it’s a red flag—especially on offshore or unlicensed platforms.