Sec-CH-UA-Mobile

The HTTP Sec-CH-UA-Mobile request header indicates whether the browser runs on a mobile device or prefers a mobile user experience.

Baseline: Limited availability

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

Table of Contents

Usage

The Sec-CH-UA-Mobile header is part of the User-Agent Client Hints framework. Servers use this header to determine whether to serve mobile-optimized layouts and content. Since Chrome's User-Agent reduction, the mobile UA string is frozen to Android 10; K regardless of actual device, making this header the reliable way to detect mobile form factor on the server side.

Browsers classify themselves as mobile or desktop based on the underlying operating system and device hardware. Mobile browsers send ?1 while desktop browsers send ?0. Desktop browsers also send ?1 when the user enables a mobile viewing mode or when browser features request mobile content rendering.

The header is a low-entropy hint sent by default on every request without requiring server opt-in through Accept-CH. Browsers send Sec-CH-UA-Mobile alongside Sec-CH-UA as part of the basic User-Agent Client Hints set. The header follows Structured Header boolean syntax with ?0 for false and ?1 for true.

Sites serving responsive layouts benefit from knowing the form factor during initial HTML generation. The header informs server-side rendering decisions, adaptive image selection, and mobile-specific feature activation. Combined with other client hints like Device-Memory, servers tailor responses to device capabilities before any JavaScript execution.

Values

?0

The browser does not prefer a mobile experience. Desktop and laptop browsers send this value.

?1

The browser prefers a mobile experience. Smartphones and tablets send this value. Desktop browsers also send ?1 when mobile emulation mode is active.

Example

A desktop Chrome browser running on Windows sends ?0 to indicate a desktop user experience.

Sec-CH-UA-Mobile: ?0

A mobile browser on an Android phone sends ?1 to request mobile-optimized content.

Sec-CH-UA-Mobile: ?1

Takeaway

The Sec-CH-UA-Mobile header sends a boolean signal indicating whether the browser runs on a mobile device, enabling servers to tailor content to device form factor.

See also

Last updated: March 6, 2026