Back to all glossary articles

User identifier (user ID)

A user identifier or user ID is a piece of information that identifies a user and distinguishes them from other users. User identifiers apply to various legal and tech concepts.

According to GDPR, any information that can lead to the direct or indirect identification of an individual will be considered personal data. The types of identifiers include a name, an identification number, location data, or an online identifier (like an IP address or cookies). These identifiers refer to information about an individual’s tools, applications, or devices. If you collect personal data, you are subject to GDPR requirements.

User identifiers also play a significant role in analytics. Many analytics technologies can’t identify unique users if they use multiple devices across multiple sessions. Each time a user does this, a new user is counted. A unique user ID eliminates this issue, attributing all activity to one user in analytics reports.

More details about the user ID on the Piwik PRO help center and blog:

  • Privacy by design in practice: How “just enough” data beats “just in case” collection

    While collecting more data “just in case” feels safer, according to Matt Gershoff, it’s also one of the biggest sources of unnecessary compliance risk, analytical noise, and wasted organizational resources in the analytics industry today. His approach of “just enough” data collection is more intentional, more aligned with privacy regulation, and often more analytically effective.

  • 4 ways to make your analytics HIPAA-compliant: Implementation guide

    Healthcare organizations have four main approaches to achieving HIPAA-compliant analytics. Each has different trade-offs in cost, technical complexity, and analytics capabilities. This guide compares all four implementation methods – from using Google Analytics with workarounds to deploying fully HIPAA-compliant analytics platforms – so you can choose the right approach for your organization’s needs and resources.

Other definitions

Recent posts from Piwik PRO blog