Are online casinos rigged? How licensed slots are tested, and where the real risks are
Licensed online slots must use random number generators that independent labs test before release. The house edge is not hidden; it is published as RTP. The real risks sit with unlicensed sites, lower RTP settings and copied games.
Key takeaways
- 01In regulated markets, slot results come from random number generators that an approved test house must check before a game is released. In Great Britain, compensated games that adjust to past results are banned.
- 02The house edge is built into every slot and published as RTP. A 96% RTP game is designed to keep about 4% of total stakes over a very large number of spins.
- 03The biggest risks are unlicensed sites, which lack regulated protections, and licensed games turning up on illegal sites through resellers, which the Gambling Commission warned about in January 2025.
- 04There is no legitimate way to cheat or find a loose online slot. Licensed outcomes cannot be influenced by stake size or style of play, and cheating at gambling is a criminal offence in Great Britain.
- 05Before playing, check the regulator’s public register and the RTP shown in the game’s own information screen.
Licensed online casinos are not rigged against individual players, but every slot they offer is designed to make money. In regulated markets, slot results must come from a random number generator (RNG) that an approved independent test house checks before release. Great Britain’s RTS 7 says results must be “acceptably random” and bans “adaptive behaviour (that is, a compensated game)”. The house edge is not hidden: it is the gap between 100% and the published return to player (RTP). The real risks are unlicensed sites, lower RTP settings and copied games.
What regulators require
| Regulator | Randomness rule | Testing rule |
|---|---|---|
| Gambling Commission (Great Britain) | RNG output should be unpredictable; compensated games banned (RTS 7) | New products tested by an approved test house before release |
| AGCO (Ontario) | Outcomes not influenced by stake size or style of play (Standard 4.26) | Mechanism must be capable of being monitored and inspected (4.27) |
| Malta Gaming Authority | RNG must comply with the Gaming Act | RNG test certificate from an independent EU/EEA-based lab |
Under the Gambling Commission’s testing strategy, licensees “must ensure that all new products have been adequately tested by an approved test house prior to release”. RNG testing covers documentation, known weaknesses in the algorithm, source code, and statistical tests on the raw output.
The Commission’s approved list, dated 2 March 2026, includes BMM Testlabs, eCOGRA, Gaming Laboratories International (GLI) and others. Each must hold ISO/IEC 17025 accreditation. GLI’s own GLI-19 standard says a game “shall not modify or discard outcomes selected by the RNG due to adaptive behavior”.
Ontario’s Standard 4.26 says outcomes “shall not be influenced, affected or controlled by the amount wagered, or by the style or method of play” unless the change is disclosed. Malta requires an RNG test certificate issued by an independent EU/EEA-based testing lab.
The house edge is built in, and published
Random does not mean even. Every slot pays back less than it takes over time, and RTP measures how much less. The Gambling Commission’s RTP guide calls it “an average achieved over a significant number of game plays and not each time the gaming machine is played”. A game at 96% RTP is designed to return about 96 of every 100 units staked over a very large number of spins and keep the other 4. Whether that is a good figure is covered in is 96% RTP good for a slot?
In Great Britain, RTS 3 requires games to show information about the chances of winning, such as RTP, before you commit to gamble.
Where the real risks are
| Risk | Why it matters | How to check |
|---|---|---|
| Unlicensed site | Payouts may be withheld or delayed; no required safer-gambling tools | Regulator’s public register |
| Lower RTP setting | Identical-looking games can have very different payback | RTP in the game’s information screen |
| Licensed games on illegal sites | Games reach unlicensed sites through resellers | Site’s licence, not the game brand |
| Copied gaming content | Named by the Commission as an illegal-market trend | Licence check before deposit |
Unlicensed sites. Ontario’s regulator warns that on unregulated sites “payouts could be withheld or delayed and your deposits may not be securely stored”. Those sites are also not required to provide safer-gambling tools.
Lower RTP settings. Harrigan and Dixon’s 2009 study of Ontario slot design documents found that “two identical looking slot machines can have very different payback percentages”. Online, the figure that applies is the one in the game you are actually playing. See RTP versions explained and the highest-paying online slots.
Licensed games on illegal sites. In January 2025 the Gambling Commission warned that “third party resellers are distributing games supplied by operators to the illegal market”. A familiar game brand on a site therefore says nothing about the site’s licence.
Copied content. In October 2025 the Commission’s director of enforcement listed “AI-generated branding, copied gaming content” among trends in the illegal market.
You cannot cheat a slot or find a loose one
The idea of a “loose” online slot, one that is due to pay or pays more at certain times, conflicts with the rules above. Great Britain bans compensated games, and RTS 7 says rules, payouts and probabilities “may not be changed while it is available for gambling” except as the game’s rules allow and as shown to the player. The RTS 7 guidance says it should be “computationally infeasible to predict what the next number will be without complete knowledge of the algorithm and seed value”.
Trying to interfere is also a crime. Under section 42 of the Gambling Act 2005, cheating at gambling, or helping someone else to cheat, carries up to two years in prison, “whether a person who cheats … improves his chances of winning anything, or … wins anything”.
How to check a site and a game
- Find the licence. The Gambling Commission says licensed businesses “must display that they are licensed and provide a link to our public register”. Check that the activities and domain names match the register. Malta’s licensee register works the same way.
- Read the game information. Open the help or paytable screen and note the RTP shown there, not a figure quoted elsewhere.
- Compare with the studio’s published versions. Our slot database lists them, but it does not inspect any individual casino’s setup.
None of these checks changes the house edge. They only confirm that you are playing the game you think you are, on a site that has to follow the rules.
Questions
Are online slots rigged?
Licensed online slots are not rigged in the sense of being secretly controlled. Regulators such as the Gambling Commission, the AGCO and the Malta Gaming Authority require random outcomes and independent testing. They do have a built-in house edge, published as RTP, so players lose money on average over time.
Can a casino change the odds while I am playing?
Not under Great Britain’s rules. RTS 7 bans compensated games that adjust to past results, and says rules, payouts and probabilities may not change while a game is available unless the game’s rules allow it and the change is shown to the player.
How do I find loose slots online?
You cannot. Ontario’s standards say outcomes must not be influenced by the amount wagered or the style of play, and Great Britain bans compensated games. The only figure that differs between games is the published RTP, which you can read in the game information.
How do I check if an online casino is licensed?
Look up the business on the regulator’s public register. The Gambling Commission says licensed businesses must display their licence and link to its register, and that the activities and domain names should match what the register shows.
Is it illegal to cheat at online slots?
In Great Britain, yes. Section 42 of the Gambling Act 2005 makes cheating, or helping someone else cheat, an offence carrying up to two years in prison, whether or not anything is won.