# Content-DPR header



The HTTP **`Content-DPR`** [response header](https://developer.mozilla.org/en-US/docs/Glossary/response%20header) is used to confirm the _image_ device to pixel ratio (DPR) in requests where the screen [DPR](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/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](https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-client-hints-07).
> The [Responsive Image Client Hints](https://wicg.github.io/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](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/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>
        [Response header](https://developer.mozilla.org/en-US/docs/Glossary/Response%20header),
        <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Client_hints">Client hint</a>
      </td>
    </tr>
    <tr>
      <th scope="row">[Forbidden request header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden%20request%20header)</th>
      <td>No</td>
    </tr>
    <tr>
      <th scope="row">
        [CORS-safelisted response header](https://developer.mozilla.org/en-US/docs/Glossary/CORS-safelisted%20response%20header)
      </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`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/DPR#examples) header example.

## Browser compatibility

## See also

- Device and responsive image client hints
  - [Sec-CH-Device-Memory](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-Device-Memory)
  - [Sec-CH-DPR](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-DPR)
  - [Sec-CH-Viewport-Height](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-Viewport-Height)
  - [Sec-CH-Viewport-Width](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-Viewport-Width)
- [Accept-CH](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-CH)
- [HTTP Caching: Vary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching#vary) and [Vary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Vary)
- [Improving user privacy and developer experience with User-Agent Client Hints](https://developer.chrome.com/docs/privacy-security/user-agent-client-hints) on developer.chrome.com (2020)