Report
Illegal online gambling: Consumer engagement and trends
The Gambling Commission’s report into estimated trends in consumer engagement with illegal gambling websites.
Annex A - Summary of approach, assumptions and caveats
Our approach is currently a methodology in development. The following summarises each stage of our approach to estimating engagement, outlines key caveats and limitations, and sets out actions we will take to make further improvements.
Identifying illegal gambling websites
Summary of approach
Search terms are used to identify illegal gambling websites. These terms are based on insight from consumer research and engagement with industry. Results obtained from search terms are checked against our register of licensed (and therefore legal) gambling opportunities. We also remove links to websites that are geo-blocked. This leaves us with a list of illegal gambling websites which are currently marketed at consumers in Great Britain.
Caveats and limitations
We believe these terms are effective at capturing the majority of illegal gambling websites given we see significant overlap in websites identified in different terms. This approach only captures illegal gambling facilitated via websites – for example it does not search Apps Stores. It captures websites that are marketed on social media – but does not identify opportunities to gambling facilitated directly within social media channels. Some websites that are geo-blocked may still be accessed by consumers in Great Britain using Virtual Private Networks (VPNs). Assumptions to account for this are outlined in the following paragraphs.
Actions to improve
We will continue to monitor research on consumer motivations and update our search terms to reflect changing trends. We also recognise the need to explore opportunities to collect data related to social media gambling (on platforms such as Telegram) and within Apps.
Estimating number of website visits and visit duration
Summary of approach
We use Similarweb to estimate the number of visits to websites identified from search terms associated with illegal gambling websites. We also obtain data on the estimated duration of these visits. Data is collected monthly.
Caveats and limitations
Web traffic intelligence platforms make estimates – and these can be subject to significant margins for error. We have made estimates of the associated margins for error and have published these.
Actions to improve
Further work is needed to understand the margins of error associated with web traffic estimates. There is an opportunity to work with licensed operators to compare the actual web traffic they experience and compare that to Similarweb estimates.
We also plan to trial other web traffic intelligence platforms and compare results from different sources.
Accounting for VPN use
Summary of approach
VPN use will conceal some web traffic – including traffic to websites that are geo-blocked to GB consumers. We use survey data to apply an uplift to account for this hidden traffic.
Caveats and limitations
The true level of activity concealed by VPNs is very difficult to know. Our survey sample is currently limited in size and associate with a wide margin for error.
Actions to improve
We will obtain more data on VPN use in larger consumer surveys.
We are also exploring how we can use open banking data to track changes in VPN subscription payments. We are also monitoring data on VPN downloads from App stores.
Estimating overall engagement
Summary of approach
We combine data on number of visits and visit duration to create an engagement metric. This can be used to represent overall engagement with illegal gambling websites.
Caveats and limitations
The engagement metric is subject to margins of error associated with both Similarweb estimates and VPN use estimates. This further widens the margin of error associated with this metric.
Actions to improve
The actions outline above will help improve confidence in the overall engagement metric estimation.
Next sectionAnnex B - Bootstrapping methodology for web traffic estimates
Last updated: 30 September 2025
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