ChromeOS user agent tokens
Chrome on ChromeOS includes a CrOS platform token with an architecture marker, distinguishing Chromebooks from other desktop platforms. The rest of the user agent follows the standard Chrome structure. ChromeOS can also run Android apps, whose web views may report Android tokens instead.
What this means
ChromeOS is Google's operating system for Chromebooks. The browser is Chrome, so the user agent follows the Chrome structure, but the platform token is CrOS together with an architecture marker rather than Windows NT, Macintosh, or X11; Linux.
The CrOS token is the reliable signal that a visit comes from a Chromebook. ChromeOS is widely deployed in education and some enterprise fleets, so meaningful CrOS share often reflects those audiences.
Android apps on ChromeOS
ChromeOS can run Android apps. When a site is opened inside an Android app's web view on a Chromebook, the request may carry Android platform tokens instead of the CrOS desktop token.
This means CrOS share can understate total Chromebook usage, because some of it arrives looking like Android. Treat the CrOS token as a confident positive signal but not a complete census of Chromebook traffic.
- Token: CrOS plus an architecture marker
- Otherwise a standard Chrome-pattern user agent
- Android web views on ChromeOS may report Android tokens
Practical handling
Surface ChromeOS as its own platform segment rather than folding it into desktop Chrome, especially if your audience includes schools. Use Client Hints (Sec-CH-UA-Platform reports the platform) for forward-compatible detection.
Do not use the platform token alone for access control; it is coarse context and client-supplied.
How it appears in analytics and logs
A Chrome-pattern user agent containing a CrOS token indicates a Chromebook running ChromeOS. Android apps on ChromeOS may instead present Android tokens, so not all ChromeOS-device traffic carries the CrOS marker.
Diagnostic use case
Identify Chromebook traffic in platform analytics, which is common in education, and avoid lumping ChromeOS into a generic Chrome-on-desktop bucket.
What WebmasterID can help detect
WebmasterID treats the CrOS token as coarse OS context, surfacing Chromebook traffic distinctly so education and managed-device audiences are visible rather than hidden inside generic Chrome.
Common mistakes
- Folding ChromeOS into generic desktop Chrome and losing Chromebook visibility.
- Assuming all Chromebook traffic carries the CrOS token.
- Treating the CrOS token as a device fingerprint.
Privacy and accuracy notes
The CrOS token is coarse OS context, not an identity. WebmasterID records the broad platform family only and never combines tokens to fingerprint a Chromebook.
Related pages
- Chrome user agent and its quirks
Chrome's user-agent string is full of historical artefacts: it claims AppleWebKit and Safari for compatibility even though Chrome uses the Blink engine. Google has also reduced the detail Chrome exposes in the UA, moving fine-grained information into User-Agent Client Hints. This page explains the pattern and the quirks.
- Android OS user agent tokens
Browsers on Android include a Linux; Android platform token with an OS version, and historically a device model identifier. With user-agent reduction, Chrome on Android now sends a generic device token instead of the real model, so model-based detection no longer works and Client Hints are needed for device detail.
- User-Agent Client Hints
User-Agent Client Hints are HTTP headers (the Sec-CH-UA family) that let a site request specific browser, platform, and version detail rather than reading it all from one passive string. They underpin UA reduction: the raw user agent is shrinking, and finer detail moves to opt-in hints. This page explains the model.
- WebmasterID docs
Coarse platform segmentation recorded 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.