ContextQMD
Back to Content

Content-DPR header

files/en-us/web/http/reference/headers/content-dpr/index.md

latest2.5 KB
Original Source

{{deprecated_header}}{{securecontext_header}}{{Non-standard_header}}

The HTTP Content-DPR {{Glossary("response header")}} is used to confirm the image device to pixel ratio (DPR) in requests where the screen {{HTTPHeader("DPR")}} client hint was used to select an image resource.

[!NOTE] The Content-DPR header was removed from the client hints specification in draft-ietf-httpbis-client-hints-07. The Responsive Image Client Hints specification proposes to replace this header by specifying intrinsic resolution/dimensions in EXIF metadata.

If the DPR client hint is used to select an image, the server must specify Content-DPR in the response. If the value in Content-DPR is different from the {{HTTPHeader("DPR")}} value in the request (i.e., image DPR is not the same as screen DPR), the client must use the Content-DPR for determining intrinsic image size and scaling the image.

If the Content-DPR header appears more than once in a message, the last occurrence is used.

<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td> {{Glossary("Response header")}}, <a href="/en-US/docs/Web/HTTP/Guides/Client_hints">Client hint</a> </td> </tr> <tr> <th scope="row">{{Glossary("Forbidden request header")}}</th> <td>No</td> </tr> <tr> <th scope="row"> {{Glossary("CORS-safelisted response header")}} </th> <td>No</td> </tr> </tbody> </table>

Syntax

http
Content-DPR: <number>

Directives

  • <number>
    • : The image device pixel ratio, calculated according to the following formula: Content-DPR = Selected image resource size / (Width / DPR)

Examples

See the DPR header example.

Browser compatibility

{{Compat}}

See also