Sec-CH-UA-Arch

The HTTP Sec-CH-UA-Arch request header indicates the CPU architecture of the platform running the browser.

Table of Contents

Baseline: Limited availability

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

Usage

The Sec-CH-UA-Arch header is part of the Client Hints infrastructure and specifically belongs to the User-Agent Client Hints family. Servers request this header by including Sec-CH-UA-Arch in the Accept-CH response header. The browser then includes the header in subsequent requests to the same origin.

This header is a high-entropy hint. Servers must explicitly opt in to receive this header through Accept-CH. The header requires HTTPS and a secure context. Browsers do not send this header automatically.

Software download sites use this header to recommend the correct binary executable for the user's system. The architecture information combines with Sec-CH-UA-Platform, Sec-CH-UA-Platform-Version, and Sec-CH-UA-Bitness to determine which build to offer. An x86 user receives different binaries than an ARM user running the same operating system.

Values

Architecture string

The value is a quoted string identifying the CPU architecture. Common values include "x86" and "arm".

The exact value depends on the underlying platform. Different operating systems report the same hardware using different identifiers.

Example

An x86-based Windows system sends "x86" to indicate the Intel or AMD processor architecture family. Bitness (32-bit vs 64-bit) is reported separately by Sec-CH-UA-Bitness. Software download pages use this to present x86 installers instead of ARM builds.

Sec-CH-UA-Arch: "x86"

An ARM-based device like a modern Mac with Apple Silicon sends "arm" to identify the processor family. Combined with bitness information, this guides servers toward ARM64 binaries.

Sec-CH-UA-Arch: "arm"

Takeaway

The Sec-CH-UA-Arch header sends CPU architecture information as a high-entropy client hint, enabling servers to recommend architecture- specific downloads and content.

See also

Last updated: March 6, 2026