The app_update event
app_update is an automatically collected GA4/Firebase event that fires when a user opens an app after it has been updated to a new version. It records the previous app version so you can see adoption of releases and behaviour changes after an update. It is distinct from first_open (a brand-new install) and app_open (any foreground), marking specifically the first launch on a new version.
What this means
In Firebase/GA4 for apps, app_update is collected automatically when a user launches the app after it has been updated. The event carries a previous_app_version parameter so you can see what version the user came from. It lets you measure release adoption and compare metrics across versions without instrumenting anything yourself.
How it differs from first_open and app_open
first_open fires once, on the very first launch after install. app_open fires whenever the app comes to the foreground. app_update sits between them: it fires on the first launch following a version update, not on a fresh install and not on every open. Tracking it lets you correlate a behaviour change with a specific release, which is invaluable when a new version introduces or fixes something.
- Auto-fires on first launch after a version update
- Carries previous_app_version
- Not first_open (install) and not app_open (any foreground)
How it appears in analytics and logs
A wave of app_update events after a release shows adoption; users who never produce one are still on an old version, which can explain version-specific bugs.
Diagnostic use case
Track how quickly users move onto a new app version and whether behaviour shifts after an update, using the automatically collected app_update event.
What WebmasterID can help detect
WebmasterID is web-first, but the principle carries over: a version/release signal is about the software, never about identifying the person running it.
Common mistakes
- Confusing app_update with first_open or app_open.
- Ignoring previous_app_version when analysing release adoption.
- Assuming all users update at the same pace.
Privacy and accuracy notes
app_update records the prior app version, not the user. Version strings are not personal data; no identifier belongs on the event. This is educational, not legal advice.
Related pages
- The os_update event
os_update is an automatically collected GA4/Firebase event fired when a user opens an app after the device's operating system has been updated to a new version. It records the previous OS version, helping you correlate behaviour or crash changes with platform updates. Like app_update it is a lifecycle signal about the environment, not the person — useful for compatibility analysis after a major OS release.
- The app_remove event (uninstalls)
app_remove is an automatically collected GA4/Firebase event indicating that an app package was removed (uninstalled) from a device, available on Android via Play. It is the closest thing to a churn signal at the device level — but it is reported with delay and is platform-limited, so it is directional, not real-time. This page covers how it works and how to read uninstall data honestly.
- 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.
- Event Explorer
Inspect app lifecycle events.
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.