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.
What this means
In Firebase/GA4 for apps, os_update is collected automatically when a user opens the app after the device's operating system has been updated. It carries a previous_os_version parameter. This lets you see how your user base moves across OS versions and whether app behaviour shifts when a platform update lands.
Why it matters for compatibility
Operating-system updates can change rendering, permissions, background limits, or APIs your app relies on. If crashes or engagement change right after an OS release, os_update events let you confirm the timing and segment affected users by OS version. That turns 'something broke last week' into 'the new OS version introduced this', which is far faster to act on. The event is environment metadata, never identity.
- Auto-fires on first launch after an OS update
- Carries previous_os_version
- Correlate OS releases with behaviour or crash changes
How it appears in analytics and logs
A cluster of os_update events near a platform release, followed by a metric shift, suggests the new OS affected your app — a compatibility lead worth investigating.
Diagnostic use case
Spot whether an OS update changed app behaviour or stability by tracking os_update and segmenting metrics by operating-system version.
What WebmasterID can help detect
WebmasterID is web-first, but the same logic holds for environment signals: record the platform version, never anything identifying the individual.
Common mistakes
- Confusing os_update (device OS) with app_update (your app).
- Ignoring previous_os_version when triaging post-update issues.
- Treating OS version as if it identified a person.
Privacy and accuracy notes
os_update records the previous OS version string, not the user. OS versions are environment data, not personal data; no identifier belongs on the event. This is educational, not legal advice.
Related pages
- 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.
- 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.
- 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.
- Event Explorer
Inspect device and 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.