Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
|Header type||Request header, Client hint|
|Forbidden header name||no|
The hint is useful when selecting image sources that best correspond to a screen's pixel density. This is similar to the role played by
x descriptors in the
srcset attribute to allow user agents to select a preferred image.
If a server uses the
DPR hint to choose which resource is sent in a response, the response must include the
Content-DPR header. The client must use the value in
Content-DPR for layout if it differs from the value in the request's
DPR header appears more than once in a message the last occurrence is used.
- Client Hints are accessible only on secure origins (via TLS).
- A server has to opt in to receive the
DPRheader from the client, by sending the
- Servers that opt in to the
DPRclient hint will typically also specify it in the
Varyheader. This informs caches that the server may send different responses based on the header value in a request.
DPRwas removed from the client hints specification in draft-ietf-httpbis-client-hints-07. The proposed replacement is
Sec-CH-DPR(Responsive Image Client Hints).
The client device pixel ratio.
A server must first opt in to receive the
DPR header by sending the response header
Accept-CH containing the directive
Then on subsequent requests the client might send
DPR header to the server:
If a request with the
DPR header (as shown above) is for an image resource, then the server response must include the
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