What it is

first_visit is an automatically collected web event in Google Analytics 4. It marks the moment GA4 recognizes a browser/device as new to your property. You don’t need to implement it manually.

When first_visit fires

On a user’s first landing page where GA4 detects no existing Client ID, GA4 creates a fresh Client ID (stored in the first-party cookie _ga) and logs first_visit. In apps, the analogous event is first_open.

Practically, this means a new browser or device, or a browser/device where cookies were cleared or blocked. It does not necessarily mean a brand-new person.

Relationship to sessions and session_start

In the initial session for a new browser/device, GA4 logs both:

• session_start — establishes the session context and assigns ga_session_id / ga_session_number.
• first_visit — classifies the user as new for this property.

They are generated at the very beginning of that first session (near-simultaneously). If you see more first_visit than session_start, treat it as a misconfiguration smell.

How it affects Users and Active Users

• New users metric. A first_visit increments New users for the selected date range.
• Active users. A user counts as active if they had an engaged session or if GA4 collected a first_visit/first_open. Thus every new user is active by definition.
• Don’t confuse the user_engagement event with the Active users metric.
• “First user …” dimensions. GA4 writes user-scoped acquisition dimensions at the time of the first session (e.g., First user source / medium / campaign).

Parameters & identifiers recorded with first_visit

Identifiers

• client_id
• ga_session_id
• ga_session_number
• user_id (optional if configured)

Page context

• page_location
• page_referrer
• page_title

Traffic & filtering

• traffic_type
• ignore_referrer

Stream-level defaults

• language
• screen_resolution

What you can (and can’t) customize

• User-ID: send user_id.
• Consent Mode (v2): cookieless pings + modeling.
• Cross-domain measurement: preserve continuity across domains.
• Internal traffic rules: populate traffic_type.
• Referrer handling: set ignore_referrer where needed.

Common pitfalls & how to fix them

1) Inflated new users

Caused by cookie deletion/blocks or misfired custom first_visit.

2) Mismatch with session_start

Caused by consent/ad-blockers or cross-domain misconfig.

3) Underreporting with Consent Mode

Cookieless pings lack IDs; fix with Advanced Consent Mode and behavioral modeling.