Secure context

This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.


This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The Accept-CH header may be set by a server to specify which client hints headers a client should include in subsequent requests.

Header type Response header
Forbidden header name no

Note: Client hints are accessible only on secure origins (via TLS). Accept-CH (and Accept-CH-Lifetime) headers should be persisted for all secure requests to ensure client hints are sent reliably.


Accept-CH: <list of client hints>


Accept-CH: Viewport-Width, Width
Vary: Viewport-Width, Width

Note: Remember to vary the response based on the accepted client hints.


Specification Title
RFC 8942: Accept-CH HTTP Client Hints

Browser compatibility

BCD tables only load in the browser

See also