Content-DPR header

Secure context

The HTTP Content-DPR response header is used to confirm the image device to pixel ratio (DPR) in requests where the screen 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 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	[Response header](https://developer.mozilla.org/en-US/docs/Glossary/Response%20header), Client hint
[Forbidden request header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden%20request%20header)	No
[CORS-safelisted response 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

See also

• Device and responsive image client hints
  • Sec-CH-Device-Memory
  • Sec-CH-DPR
  • Sec-CH-Viewport-Height
  • Sec-CH-Viewport-Width
• Accept-CH
• HTTP Caching: Vary and Vary
• Improving user privacy and developer experience with User-Agent Client Hints on developer.chrome.com (2020)