HTTP Headers
Sec CH UA Arch
HTTP Header
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The HTTP <code>Sec-CH-UA-Arch</code> request header is a user agent client hint which contains the user-agent’s underlying CPU architecture, such as ARM or x86.
This might be used by a server, for example, to select and offer the correct binary format of an executable for a user to download.
| Header type | Request header, Client hint |
|---|---|
| Forbidden request header | Yes (Sec- prefix) |
Syntax
Syntax
http
Sec-CH-UA-Arch: <arch>Directives
Directives
- arch
A string specifying the underlying platform architecture, such as: “x86”, “ARM”, or a list like “[arm64-v8a, armeabi-v7a, armeabi]”.
Example
Using Sec-CH-UA-Arch
A server can request the Sec-CH-UA-Arch header by including the Accept-CH directive in its response, specifying the desired header as a token:
http
HTTP/1.1 200 OK
Accept-CH: Sec-CH-UA-Arch
The client may choose to provide this header in subsequent requests. For example, on a Windows X86-based computer, the client might include the header as shown:
http
GET /my/page HTTP/1.1
Host: example.site
Sec-CH-UA: " Not A;Brand";v="99", "Chromium";v="96", "Google Chrome";v="96"
Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Platform: "Windows"
Sec-CH-UA-Arch: "x86"
Note that the high entropy headers like Sec-CH-UA and Sec-CH-UA-Platform are included automatically, even if not explicitly requested by the server.
How to Modify Header using Requestly
Requestly is a powerful Chrome extension that allows you to modify HTTP headers, including the Sec-CH-UA-Arch header. This is helpful when you want to test how your website or application behaves on different device architectures without needing actual hardware. Steps to Modify the Sec-CH-UA-Arch Header:
- Install and open the Requestly Chrome extension. You can find it on the Chrome Web Store.
- Create a new rule: Click on “Create Rule” and choose “Modify Headers” from the list of available rule types.
- Add a new header modification:
- Under “Action”, select “Add” or “Override”.
- In the “Header Name” field, enter Sec-CH-UA-Arch.
- In the “Header Value” field, enter the architecture value you want to simulate (e.g., x86, arm).
- Set the URL condition: Specify the URL or pattern where this header change should apply (e.g., https://your-api.com/*).
- Save the rule.
Once set up, Requestly will inject the Sec-CH-UA-Arch header with your specified value into matching requests, enabling you to test how your server or application reacts to different client architectures.
Modifying the Sec-CH-UA-Arch header is useful because it helps developers ensure their sites work correctly across different hardware platforms by simulating requests as if they came from those platforms.
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