Sec-CH-DPR header

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The HTTP Sec-CH-DPR request header provides device client hints about the client device pixel ratio (DPR). This ratio is the number of physical device pixels corresponding to every CSS 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 by x descriptors in the <img> srcset attribute to allow user agents to select a preferred image.

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

Servers that opt in to the Sec-CH-DPR client hint will typically also specify it in the Vary header to inform caches that the server may send different responses based on the header value in a request.

Header type	Request header, Client hint
Forbidden request header	No

Syntax

http

Sec-CH-DPR: <number>

Directives

<number>: The client device pixel ratio.

Examples

A server must first opt in to receive the Sec-CH-DPR header by sending the response header Accept-CH containing the directive Sec-CH-DPR.

http

Accept-CH: Sec-CH-DPR

Then on subsequent requests the client might send Sec-CH-DPR header to the server:

http

Sec-CH-DPR: 2.0

Specifications

Specification
Responsive Image Client Hints # sec-ch-dpr

Browser compatibility

	desktop					mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`Sec-CH-DPR` request header Experimental	Chrome – Full support Chrome 46 (Release date: 2015-10-13) altname altname Alternate name: DPR Chrome – Full support Chrome 97 (Release date: 2022-01-04) footnote Full support	Edge – Full support Edge 79 (Release date: 2020-01-15) altname altname Alternate name: DPR Edge – Full support Edge 97 (Release date: 2022-01-06) footnote Full support	Firefox – No support Firefox footnote No support	Opera – Full support Opera 33 (Release date: 2015-10-27) altname altname Alternate name: DPR Opera – Full support Opera 83 (Release date: 2022-01-19) footnote Full support	Safari – No support Safari footnote No support	Chrome Android – Full support Chrome Android 46 (Release date: 2015-10-14) altname altname Alternate name: DPR Chrome Android – Full support Chrome Android 97 (Release date: 2022-01-04) footnote Full support	Firefox for Android – No support Firefox for Android footnote No support	Opera Android – Full support Opera Android 33 (Release date: 2015-11-03) altname altname Alternate name: DPR Opera Android – Full support Opera Android 68 (Release date: 2022-03-30) footnote Full support	Safari on iOS – No support Safari on iOS footnote No support	Samsung Internet – Full support Samsung Internet 5 (Release date: 2016-12-15) altname altname Alternate name: DPR Samsung Internet – Full support Samsung Internet 18 (Release date: 2022-08-08) footnote Full support	WebView Android – Full support WebView Android 46 (Release date: 2015-10-14) altname altname Alternate name: DPR WebView Android – Full support WebView Android 97 (Release date: 2022-01-04) footnote Full support	WebView on iOS – No support WebView on iOS footnote No support

Tip: you can click/tap on a cell for more information.

Full support: Full support
No support: No support
: Experimental. Expect behavior to change in the future.
: Uses a non-standard name
: Has more compatibility info.

Sec-CH-DPR header

Syntax

Directives

Examples

Specifications

Browser compatibility

Legend

See also