Report
Illegal online gambling: Consumer engagement and trends
The Gambling Commission’s report into estimated trends in consumer engagement with illegal gambling websites.
Part 3 - Measuring engagement with the online illegal market
Key point summary
Key points in this section are as follows:
- we use Similarweb, a web intelligence platform, to estimate web traffic associated with the illegal gambling websites identified through the methodology set out in Part 2
- we obtain estimates of the number of visits to these websites and the duration of these visits
- web traffic estimates are imprecise, so results need to be treated with caution. Variability in these web traffic data was estimated using nonparametric 95 percent confidence intervals from 1,000 bootstrap samples
- the data we have collected shows estimated numbers of visits fluctuating over the 15 months monitored. More data needs to be collected, over a longer period, to understand if observed effects reflect seasonal changes or longer-term trends
- the duration of visits remained relatively constant over the period monitored.
Interpreting web traffic estimates
Once a list of illegal gambling websites has been identified, we want to understand the number of visits from consumers in Great Britain associated with each website. Similarweb is a third-party web intelligence platform used to access web traffic data with identified websites. The data obtained through Similarweb is based on estimations and helps us understand volume and changes in website engagement. More details on the methodology for calculating these estimates can be found on the Similarweb website (opens in a new tab) .
Estimated web traffic involves inherent uncertainty, particularly when relying on third-party data sources that use indirect measurement techniques. To better understand and communicate this uncertainty, we applied a bootstrapping approach to 2 key metrics: average estimated visits per site and average duration per visit per site.
By quantifying the range within which the true values are likely to fall this method provides a more transparent view of the variability in the data, helping to avoid overconfidence in point estimates. Further details of our approach to this analysis are provided in Annex B.
Despite the uncertainty around these estimations, they provide insights that allow us to start understanding the scale of the illegal gambling market. They also enable the targeted disruption of the illegal gambling websites that are most likely to be experiencing high levels of user engagement – and to measure the impact of the disruption work we undertake.
Data collected on estimated number of visits to illegal gambling websites
Estimated visits made by consumers in Great Britain increased between August and December 2024.This growth levelled out and was followed by a relatively sharp decrease in February 2025. By July 2025, estimated visits had returned to broadly similar levels to July 2024.
The following chart, and further charts in this report, include a 95 percent confidence interval calculated using the bootstrap analysis outlined in the previous section.
Figure 3: Estimated visits to illegal websites
| Date | Visits (upper bound) (millions) |
Visits (point estimate) (millions) |
Visits (lower bound) (millions) |
|---|---|---|---|
| May 2024 | 54 | 36 | 21 |
| June 2024 | 31 | 20 | 12 |
| July 2024 | 22 | 16 | 11 |
| August 2024 | 27 | 20 | 13 |
| September 2024 | 29 | 21 | 15 |
| October 2024 | 43 | 29 | 18 |
| November 2024 | 55 | 35 | 21 |
| December 2024 | 46 | 36 | 27 |
| January 2025 | 45 | 36 | 29 |
| February 2025 | 32 | 25 | 19 |
| March 2025 | 30 | 23 | 18 |
| April 2025 | 28 | 21 | 14 |
| May 2025 | 21 | 17 | 14 |
| June 2025 | 21 | 17 | 13 |
| July 2025 | 24 | 20 | 16 |
Data collected on estimated average visit duration
Estimated average visit duration has also been collected from Similarweb for each illegal website that we identified. When averaging across all sites, this has remained relatively consistent around 6 and 7 minutes per visit since we started collecting the data.
Figure 4: Estimated visit duration on illegal websites
| Date | Mean visit duration (upper bound) (Minutes) |
Mean visit duration (point estimate) (Minutes) |
Mean visit duration (lower bound) (Minutes) |
|---|---|---|---|
| May 2024 | 7 | 6 | 5 |
| June 2024 | 7 | 6 | 5 |
| July 2024 | 8 | 7 | 6 |
| August 2024 | 7 | 6 | 5 |
| September 2024 | 8 | 7 | 5 |
| October 2024 | 6 | 5 | 5 |
| November 2024 | 6 | 5 | 5 |
| December 2024 | 7 | 6 | 5 |
| January 2025 | 7 | 6 | 5 |
| February 2025 | 7 | 6 | 5 |
| March 2025 | 7 | 6 | 5 |
| April 2025 | 7 | 6 | 5 |
| May 2025 | 7 | 6 | 5 |
| June 2025 | 6 | 5 | 5 |
| July 2025 | 6 | 6 | 5 |
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Last updated: 30 September 2025
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