first_open vs first_visit
first_open and first_visit are the new-user events in GA4, split by platform: first_open fires on the first launch of an app after install, while first_visit fires on a user's first visit to a website. They play the same role — establishing a user as new — but trigger on different platforms and signals. Confusing them, or comparing them across app and web, leads to misread new-user numbers.
What this means
first_open is an automatically collected app event fired the first time a user opens an app after installing it (or after analytics is enabled). first_visit is the web equivalent, fired the first time a user visits a website with analytics and storage available. Both establish the user as new and feed the new-versus-returning split, but each belongs to its own platform.
Why the distinction matters
On a combined app+web property, new users come from two different events with two different triggers: an install (first_open) and a first website visit (first_visit). Reading them as interchangeable, or summing them naively, can over- or under-state genuine new users — a person who installs the app and also visits the web could fire both. And first_visit, depending on a storage marker, re-fires when storage is cleared. Treat each as platform-specific and directional.
- first_open = first app launch after install
- first_visit = first website visit
- Platform-specific; do not treat as interchangeable
How it appears in analytics and logs
first_open spikes track installs; first_visit spikes track new web visitors. Mixing them, or comparing across platforms, misstates how many new users you truly gained.
Diagnostic use case
Read new-user counts correctly across app and web by knowing first_open is the app event and first_visit is the web event, triggered differently.
What WebmasterID can help detect
WebmasterID derives new-versus-returning for web from first-party signals only, the same first_visit role, without third-party cookies or cross-site identity.
Common mistakes
- Treating first_open and first_visit as the same event.
- Summing them into one new-user count without dedup thought.
- Ignoring storage clearing re-firing first_visit.
Privacy and accuracy notes
Both events rely on a first-party install/storage marker, not a cross-site profile. New-user status is a coarse local distinction needing no personal data. This is educational, not legal advice.
Related pages
- The first_visit event and new users
The first_visit event is fired the first time a user opens your site in a browser. It is how GA4 distinguishes new users from returning ones: the presence of a first_visit defines a new user. Because it depends on a stored marker, clearing cookies or using a fresh browser makes the same person look new — a limitation worth understanding before trusting new-user counts.
- The app_open event
app_open is a GA4 event collected automatically by the Firebase/GA4 SDK when a user opens an app or brings it to the foreground after it was in the background. It marks app launches and returns, underpinning app engagement, retention, and session analysis — but a foreground event is not the same as meaningful use.
- The session_start event
The session_start event marks the beginning of a visit. In GA4 it is fired automatically the first time a user is active in a new session, and it underpins every session-scoped metric. Understanding when a session begins — and the timeout that ends it — explains why session counts behave the way they do across midnight, campaigns, and idle periods.
- Web analytics
New-vs-returning from first-party signals.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.