Sec-CH-UA-Platform

The HTTP Sec-CH-UA-Platform request header sends the operating system or platform name 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 header is a low-entropy client hint sent by default in requests from supporting browsers. The header exposes basic platform information without requiring server opt-in through Accept-CH, making the data immediately available for adaptive content delivery.

Browsers send a quoted string indicating the platform name, such as "Windows", "macOS", "Android", or "Linux". This header works alongside Sec-CH-UA and Sec-CH-UA-Mobile as one of three low-entropy User-Agent Client Hints sent by default. Since Chrome's User-Agent reduction, the UA string freezes platform tokens to fixed values like Windows NT 10.0, making Sec-CH-UA-Platform the structured replacement for server-side platform detection.

Servers commonly use Sec-CH-UA-Platform to tailor interface elements to match platform conventions, adjust download links to offer the correct installer, or serve platform-specific instructions. The header enables content negotiation based on operating system without parsing complex User-Agent strings.

Values

Platform name

The value is a quoted string representing the operating system. Common values include:

  • "Windows" for Windows operating systems
  • "macOS" for Apple macOS
  • "Android" for Android devices
  • "Linux" for Linux-based systems
  • "Chrome OS" for ChromeOS devices
  • "iOS" for Apple iOS
  • "Unknown" when the platform cannot be determined

The value is always enclosed in double quotes and sent as a Structured Field String (sf-string).

Example

A browser running on Windows 11 sends the platform hint along with other low-entropy User-Agent client hints. The server receives platform information without requiring explicit opt-in.

Sec-CH-UA: "Chromium";v="130", "Google Chrome";v="130"
Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Platform: "Windows"

A browser running on macOS sends the platform identifier for a Mac-based system. This enables the server to provide macOS-specific download links or styling.

Sec-CH-UA-Platform: "macOS"

An Android device identifies the platform, allowing the server to serve mobile-optimized resources or redirect to an app store.

Sec-CH-UA-Platform: "Android"

Takeaway

The Sec-CH-UA-Platform header provides basic operating system information through a low-entropy client hint sent by default in Chromium-based browsers, enabling platform-aware content delivery without exposing detailed device fingerprinting data.

See also

Last updated: March 6, 2026