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.
Sec-CH-UA user agent client hint request header provides the user-agent's branding and significant version information.
|Header type||Request header, Client hint|
|Forbidden header name||yes|
Sec-CH-UA header provides the brand and significant version for each brand associated with the browser in a comma-separated list.
A brand is a commercial name for the user agent like: Chromium, Opera, Google Chrome, Microsoft Edge, Firefox, and Safari. A user agent might have several associated brands. For example, Opera, Chrome, and Edge are all based on Chromium, and will provide both brands in the
The significant version is the "marketing" version identifier that is used to distinguish between major releases of the brand. For example a Chromium build with full version number "96.0.4664.45" has a significant version number of "96".
The header therefore allows the server to customize its response based on both shared brands and on particular customizations in their respective versions.
Sec-CH-UA is a low entropy hint. Unless blocked by a user agent permission policy, it is sent by default, without the server opting in by sending
The header may include "fake" brands in any position and with any name. This is a feature designed to prevent servers from rejecting unknown user agents outright, forcing user agents to lie about their brand identity.
Sec-CH-UA-Full-Version-List is the same as
Sec-CH-UA, but includes the full version number rather than the significant version number for each brand.