Platform dimension (web, Android, iOS)
Platform is the dimension that labels the broad surface an event came from — web, Android, or iOS — based on which data stream collected it. In a property that mixes a website and apps, it is the first cut for comparing surfaces. It is coarser than device category (which splits desktop/mobile/tablet within web) and complements the data stream ID, which is the precise per-stream key.
What this means
The platform dimension classifies each event as web, Android, or iOS according to the data stream that collected it. In a mixed property it is the cleanest first split between your website and your apps, before drilling into device or OS detail.
For a web-only property, platform is effectively always web.
How it relates to neighbours
Platform is broader than device category, which subdivides web traffic into desktop, mobile, and tablet — a mobile-web visit is platform 'web', not 'Android' or 'iOS'. It is also coarser than the data stream ID, which uniquely keys each individual stream. Use platform for the headline web/app cut, device category for browser form-factor, and stream ID for exact source.
Confusing platform with device category is a frequent reporting error.
- Web / Android / iOS by originating stream
- Coarser than device category and stream ID
- Mobile web is platform 'web', not 'iOS/Android'
How it appears in analytics and logs
A platform value is the broad surface of an event. iOS or Android values appearing in a web-only property usually mean an app stream was added that you did not expect.
Diagnostic use case
Use platform as the top-level split between web, Android, and iOS in a property that collects from both a website and mobile apps.
What WebmasterID can help detect
WebmasterID can attribute events to their broad surface first-party, so web-versus-app comparison works without third-party tracking.
Common mistakes
- Confusing platform with device category.
- Reading mobile-web as an app platform value.
- Ignoring an unexpected app stream behind iOS/Android values.
Privacy and accuracy notes
Platform records a broad surface category, not identity. WebmasterID treats platform as first-party site/app context, never as a personal identifier.
Related pages
- 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.
- Data stream ID dimension
Data stream ID is the dimension that records the numeric identifier of the GA4 data stream an event came from. A GA4 property can have web, Android, and iOS streams, and each event is stamped with its origin stream_id. It is the stable machine key for splitting reports by platform source, distinct from the editable stream name. It is configuration metadata, not anything about the visitor.
- 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 web and app surfaces first-party.
Sources and verification notes
- Google Analytics Help — [GA4] Dimensions, metrics, and other termsLists the platform dimension (web/Android/iOS).
- GA4 Data API — Schema (dimensions)Documents platform alongside stream and device dimensions.
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.