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Content-DPR header

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

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

[!NOTE]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")}}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.

Header type {{Glossary("[Response header")}}header](https://developer.mozilla.org/en-US/docs/Glossary/Response%20header), Client hint
{{Glossary("[Forbidden request header")}}header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden%20request%20header) No
{{Glossary("[CORS-safelisted response header")}}header](https://developer.mozilla.org/en-US/docs/Glossary/CORS-safelisted%20response%20header) No

Syntax

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