How to randomise the visitor config_id for privacy

From Matomo 5.5.0-b2, a new config_id randomisation setting is available to enhance privacy controls. The config_id is a unique identifier derived from browser and system configurations.

When this new setting is enabled, Matomo no longer uses user-agent data to generate the config_id. However, user-agent data is still collected for reporting purposes, such as detecting the user’s browser version, language, and screen resolution.

When admin users activate this setting globally, Matomo will generate a random config_id per tracking request to minimise user identification by ensuring there is no continuity between visits and actions. This reduces the granularity of visitor tracking but ensures compliance with strict privacy regulations. A new visit is created for every tracked action.

By default, config_id randomisation is disabled and standard tracking occurs. Matomo assigns the same config_id to a visitor to track all their requests such as page views and events which are grouped under the same visit.

How to apply the config_id randomisation setting in the UI

1. Navigate to Matomo settings (Administration) > Privacy > Anonymize Data.
2. Locate the option, Randomize config_id for enhanced privacy.
3. Check the box to apply this setting across all tracked sites.
4. Click Save and confirm the change by entering your admin password.

How does config_id randomisation affect analytics data?

Enabling config_id randomisation means each tracking request generates a new config_id, making it harder to track returning visitors or associate multiple actions with the same user session. This can lead to higher reported visit counts and reduced accuracy in visitor-based reports.

Setting enabled:

• The Visits Log displays each tracking request as a new visit.
• The log_visit database table stores unique config_id value for each request.
• Features like Funnels and Goal tracking may be impacted because visits will appear as separate, unrelated interactions rather than as a continuous session.

Setting disabled:

• Tracking requests are associated with the same visitor, maintaining session consistency.
• The Visit Log groups actions under a single visitor profile, providing a connected session history.

How does config_id randomisation affect performance?

Matomo optimises visit grouping by efficiently recognising returning visitors based on config_id. When fewer data points are available due to randomisation, Matomo must handle a larger number of individual visits, which can impact performance, particularly on high-traffic websites.

Why is this feature available?

This feature is part of Matomo’s broader privacy-focused settings, allowing organisations to adjust tracking behaviour based on their compliance requirements. It is designed to limit user identification and tracking persistence by reducing the effectiveness of config_id as a unique identifier. When enabled, Matomo will not group actions under a single visitor profile.