DPR header

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 thecompatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

Secure context: This feature is available only insecure contexts (HTTPS), in some or allsupporting browsers.

Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.

Warning:TheDPR header was removed from the client hints specification indraft-ietf-httpbis-client-hints-07.The proposed replacement isSec-CH-DPR (Responsive Image Client Hints).

The HTTPDPRrequest header providesdevice client hints about the client device pixel ratio (DPR).This ratio is the number of physical device pixels corresponding to everyCSS pixel.

The hint is useful when selecting image sources that best correspond to a screen's pixel density.This is similar to the role played byx descriptors in the<img>srcset attribute to allow user agents to select a preferred image.

If a server uses theDPR hint to choose which resource is sent in a response, the response must include theContent-DPR header.The client must use the value inContent-DPR for layout if it differs from the value in the request'sDPR header.If theDPR header appears more than once in a message the last occurrence is used.

Servers that opt in to theDPR client hint will typically also specify it in theVary header to inform caches that the server may send different responses based on the header value in a request.