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

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
CORS-safelisted response header 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: <comma separated list of client hint headers>


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

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


HTTP Client Hints
# section-3.1

Browser compatibility

BCD tables only load in the browser

See also