Google Analytics 4 (GA4) introduced an entirely new vocabulary alongside its event-based data model. Terms like "Key Event," "Engaged Session," "Predictive Audience," and "Data Stream" have no direct equivalent in the old Universal Analytics — and even familiar words like "Conversion" now mean something subtly different. Whether you're a marketer, analyst, developer, or business owner, this glossary gives you a single reference point for every GA4 term you'll encounter.
All 187 terms are arranged alphabetically with plain-English definitions. Where a term benefits from a concrete example, one is included. Use the search box or the letter navigation to jump straight to any term.
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Frequently Asked Questions
GA4 (Google Analytics 4) is Google's current web and app analytics platform, launched in 2020. It uses a fully event-based data model — tracking individual interactions like page_view, scroll, and purchase — rather than the session/hit model used by Universal Analytics (UA), which was sunset on 1 July 2023. GA4 supports both web and mobile app tracking within a single property via linked data streams.
Active Users are those who had at least one engaged session (lasting 10+ seconds, containing a key event, or including 2+ page views). Total Users counts every user who triggered any event at all, regardless of engagement. Active Users is GA4's primary headline metric; Total Users is always greater than or equal to Active Users. This was a significant shift from Universal Analytics, which reported "Users" similarly to today's Total Users.
Google renamed Conversions to Key Events in GA4 in 2024. A Key Event is any event you mark as high business value — such as purchase, sign_up, or contact_form_submit. The rename was intended to distinguish GA4's on-site measurement from the "Conversions" metric in Google Ads, which imports Key Events from GA4 and applies its own attribution modelling. The term "Conversions" still appears in Google Ads, which is a common source of confusion.
A User is an individual visitor assigned a unique identifier (Client ID for anonymous visitors, User ID for logged-in users). A Session is a group of interactions by that user within a time window — a single user can generate many sessions over days or weeks. In GA4, a session begins with a session_start event and expires after 30 minutes of inactivity or at midnight. One user visiting on Monday, then again on Wednesday, counts as 1 user but 2 sessions.
UTM (Urchin Tracking Module) parameters are tags you append to URLs so GA4 can identify exactly where traffic originated. The five standard parameters are utm_source, utm_medium, utm_campaign, utm_content, and utm_term. Without them, GA4 cannot distinguish traffic from an email campaign versus a social post — both would appear as Direct or Referral depending on how the link was clicked. Consistent UTM tagging is essential for accurate attribution reporting.
BigQuery Export streams or daily-batches all raw event-level GA4 data into a linked Google BigQuery project. Unlike GA4's standard reports — which can be sampled, are limited to 14 months of data, and aggregate data — BigQuery contains every individual event row with all parameters, at full fidelity, with no retention limit. This enables advanced SQL analysis, joining with CRM or ad cost data, and building models that are impossible in GA4's standard UI. BigQuery Export is available on free GA4 properties with a daily row limit; GA4 360 removes that limit.