files/zh-cn/web/http/headers/dpr/index.html


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---
title: DPR
slug: Web/HTTP/Headers/DPR
translation_of: Web/HTTP/Headers/DPR
---
<div>{{HTTPSidebar}}{{securecontext_header}}{{SeeCompatTable}}</div>

<p><code><strong>DPR</strong></code>请求头是<font><font>“ </font></font><font><font><a href="/zh-CN/docs/Glossary/Client_hints">客户端提示”</a>消息头，它代表客户端设备的像素比</font></font>({{Glossary("DPR")}})<font><font>，该比例是与每个CSS像素相对应的物理设备像素的数量。</font></font></p>

<table class="properties">
 <tbody>
  <tr>
   <th scope="row">Header type</th>
   <td>{{Glossary("Request header")}}</td>
  </tr>
  <tr>
   <th scope="row">{{Glossary("Forbidden header name")}}</th>
   <td>?</td>
  </tr>
 </tbody>
</table>

<div class="blockIndicator note">
<p><strong>Note:</strong> Client Hints are accessible only on secure origins (via TLS). Server has to opt in to receive <code>DPR</code> header from the client by sending {{HTTPHeader("Accept-CH")}} and {{HTTPHeader("Accept-CH-Lifetime")}} response headers.</p>
</div>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">DPR: &lt;number&gt;
</pre>

<h2 id="示例">示例</h2>

<p>Server first needs to opt in to receive <code>DPR</code> header by sending the response headers {{HTTPHeader("Accept-CH")}} containing <code>DPR</code> and {{HTTPHeader("Accept-CH-Lifetime")}}.</p>

<pre>Accept-CH: DPR
Accept-CH-Lifetime: 86400
</pre>

<p>Then on subsequent requests the client might send <code>DPR</code> header back:</p>

<pre>DPR: 1.0
</pre>

<h2 id="浏览器兼容">浏览器兼容</h2>

<p>{{Compat("http.headers.DPR")}}</p>

<h2 id="参见">参见</h2>

<ul>
 <li>{{HTTPHeader("Accept-CH")}}</li>
 <li>{{HTTPHeader("Accept-CH-Lifetime")}}</li>
 <li>{{HTTPHeader("Vary")}}</li>
</ul>