Sec-CH-UA-Platform-Version

The HTTP Sec-CH-UA-Platform-Version request header sends the operating system version number from a browser to the server as part of the Client Hints infrastructure.

Baseline: Limited availability

Supported in Chromium-based browsers (Chrome, Edge, Opera). webstatus.dev

Table of Contents

Usage

The Sec-CH-UA-Platform-Version header is a high-entropy client hint requiring explicit server opt-in through the Accept-CH response header. Unlike low-entropy hints such as Sec-CH-UA-Platform, this header exposes detailed version information increasing the fingerprinting surface, so browsers send the header only when the server requests access.

The header value is a quoted string containing the platform version in dot-separated format, such as "15.0.0" for macOS or "10.0.0" for Windows. The version string provides major, minor, and patch components when available. Some platforms return empty strings when version information is unavailable.

Since Chrome's User-Agent reduction, the UA string freezes platform tokens to fixed values like Windows NT 10.0 regardless of actual OS version. Server-side code previously extracting OS version from the User-Agent string now needs to request Sec-CH-UA-Platform-Version through Accept-CH.

Servers use Sec-CH-UA-Platform-Version to detect specific operating system versions for compatibility checks, security advisories, or feature detection. A web application might warn about known issues in a particular Windows version or enable features introduced in recent macOS releases.

Values

Platform version string

The value is a quoted string representing the operating system version. The format varies by platform:

  • Windows 10: Chromium maps each release to a major version. "0.0.0" = 1507, "1.0.0" = 1511, "2.0.0" = 1607, "3.0.0" = 1703, "4.0.0" = 1709, "5.0.0" = 1803, "6.0.0" = 1809, "7.0.0" = 1903/1909, "8.0.0" = 2004/20H2, "9.0.0" = 21H1, "10.0.0" = 21H2/22H2. Windows 11: "13.0.0" = 21H2, "14.0.0" = 22H2/23H2, "15.0.0" = 24H2
  • macOS: "15.0.0" format with major, minor, and patch components
  • Android: Version string from the native OS, such as "13.0.0"
  • Linux: Returns an empty string
  • Chrome OS: platform-specific version string

The version string follows a three-component dot-separated pattern when platform APIs provide the information. Some platforms return empty strings when version details are not exposed.

Example

A server requests platform version information through the Accept-CH response header. On subsequent requests, the browser includes the detailed version data.

Accept-CH: Sec-CH-UA-Platform-Version

A browser running macOS 15 Sequoia sends the version string with all three components. The server uses this to detect OS-level capabilities or compatibility requirements.

Sec-CH-UA-Platform-Version: "15.0.0"

A Windows 11 browser sends the platform version after receiving Accept-CH opt-in. Chromium reports Windows 11 as major version 13 and above, distinguishing Windows 11 from Windows 10 (versions 1 through 10).

Sec-CH-UA-Platform-Version: "14.0.0"

Takeaway

The Sec-CH-UA-Platform-Version header provides detailed operating system version information through a high-entropy client hint requiring server opt-in via Accept-CH, enabling precise platform detection for compatibility and feature management.

See also

Last updated: March 6, 2026