Platform dimension: web, Android, or iOS
Platform is the dimension that records the broad surface a hit came from: web, Android, or iOS. In GA4 it is determined by the data stream the event arrived through, since a property can combine app and web streams. It is coarser than the operating-system dimension and is the right axis for comparing app versus web behaviour — but mixing app-only and web-only metrics across platforms is a frequent reporting error.
What this means
A GA4 property can contain several data streams — a website stream and one or more app streams. The platform dimension records which kind produced each event: 'web', 'Android', or 'iOS'. It is set by the stream, not inferred per request.
This lets a single property report on a product that spans app and web while still being able to separate the two.
Platform is not operating system
Platform is deliberately coarse. The operating-system dimension is finer (it distinguishes Windows, macOS, ChromeOS within web, and OS versions within apps). Use platform to answer 'app vs web'; use operating system to answer 'which OS'.
The classic mistake is comparing metrics that only exist on one platform — some events are app-only (firebase events) or web-only — which produces misleading per-platform charts when a metric is structurally absent on one side.
- Set per data stream: web / Android / iOS
- Coarser than the operating-system dimension
- Beware metrics that exist on only one platform
How it appears in analytics and logs
A platform value tells you which stream type produced the data — web, Android, or iOS. Unexpected platform splits usually reflect how data streams are configured, not a behaviour change.
Diagnostic use case
Use platform to compare app and web surfaces in one property, while avoiding metrics that exist only on one platform when slicing by it.
What WebmasterID can help detect
WebmasterID distinguishes surfaces from first-party signals, so web and app traffic can be compared without invasive device identification.
Common mistakes
- Confusing platform (web/app) with operating system.
- Comparing a metric across platforms where it exists on only one.
- Assuming platform is inferred per request rather than per stream.
Privacy and accuracy notes
Platform is a coarse technical attribute of the stream, not personal data. WebmasterID records surface type first-party without device fingerprinting.
Related pages
- Operating system dimension
The operating system dimension records the platform a visit ran on: Windows, macOS, iOS, Android, Linux, ChromeOS. It is parsed from the user-agent string (and the sec-ch-ua-platform Client Hint), making it a classification rather than a reported fact. Frozen OS versions, iPadOS reporting as macOS, and webviews are the usual reasons it does not perfectly match reality.
- Screen name dimension: the app analog of page title
Screen name is the dimension that records which screen of a mobile app a user viewed — the app analog of the page-path or page-title dimension on the web. GA4 captures it from the screen_view event's screen_name and screen_class parameters. Unlike web pages, which expose a URL automatically, app screens carry no inherent name, so screen name is only meaningful when the app explicitly sets it.
- Device category: desktop, mobile, tablet
Device category groups visits into desktop, mobile, or tablet. It is derived from the user-agent string (increasingly, User-Agent Client Hints), so it is a classification, not a hardware fact. Tablets, desktop-mode mobile browsers, and foldables blur the boundaries, and the user agent can be spoofed.
- Multi-site analytics
Compare surfaces and properties in one view.
Sources and verification notes
- Google Analytics Help — [GA4] About data streamsExplains web/Android/iOS streams that set the platform dimension.
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.