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.
What this means
The operating system dimension is assigned by parsing the user-agent string into a platform family and version. With User-Agent Reduction, browsers increasingly expose the platform through the sec-ch-ua-platform Client Hint instead of detailed UA tokens.
Why it misleads
OS version detail is being frozen by UA reduction, so the reported version may be a fixed value. iPadOS presents a desktop-class user agent and can be classified as macOS. In-app webviews inherit the host OS but can mask the browser, and bots often send synthetic or blank platform tokens. Read OS as a support-prioritisation signal, not a precise platform census.
- Parsed from user agent / sec-ch-ua-platform
- iPadOS can be classified as macOS
- UA reduction freezes reported OS versions
How it appears in analytics and logs
An OS value is the parser's reading of the user agent or platform hint. An unexpected OS mix usually reflects a parsing edge case rather than a real platform shift.
Diagnostic use case
Use OS to prioritise platform support and QA, treating it as a UA-derived estimate and expecting some platforms (notably iPadOS) to be misreported.
What WebmasterID can help detect
WebmasterID derives OS family from the user agent privacy-safely and keeps bot user agents in a separate bucket, so the OS breakdown reflects human visitors.
Common mistakes
- Trusting OS minor-version detail after UA reduction.
- Missing that iPadOS may appear as macOS.
- Ignoring synthetic platform tokens from bots.
Privacy and accuracy notes
OS is read from the user agent / platform hint, a low-entropy signal, not from fingerprinting. WebmasterID classifies it without high-entropy device probing.
Related pages
- Browser dimension and its limits
The browser dimension records which browser a visit used — Chrome, Safari, Firefox, Edge, and so on. It is parsed from the user-agent string (and increasingly User-Agent Client Hints), so it is a classification, not a fact reported by the device. UA freezing, Chromium-based browsers sharing tokens, and in-app webviews are why this dimension is fuzzier than it looks.
- 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.
- Sec-CH-UA-Platform and Sec-CH-UA-Mobile
Sec-CH-UA-Platform and Sec-CH-UA-Mobile are User-Agent Client Hint request headers. Platform reports the operating-system family (such as Windows, macOS, or Android) and Mobile is a boolean for whether the client is a mobile device. Both are low-entropy hints sent by default in supporting Chromium browsers, offering coarse context without parsing the legacy user agent.
- Privacy-first analytics
Platform classification without fingerprinting.
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.