---
title: NetworkInformation.downlink
slug: Web/API/NetworkInformation/downlink
translation_of: Web/API/NetworkInformation/downlink
---
<p>{{SeeCompatTable}}{{APIRef("Network Information API")}}</p>

<p><strong><code>downlink</code></strong> 是 {{domxref("NetworkInformation")}} 接口的一个只读属性，返回以Mb/s为单位的有效带宽，并保留该值为25kb/s的最接近的整数倍。该值基于最近监测的保持活跃连接的应用层吞吐量，排除了到私有地址空间的连接。当缺少最近的带宽测量数据时，该属性由底层连接技术属性决定。</p>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">var <em>downLink</em> = NetworkInformation.downlink</pre>

<h3 id="Value">Value</h3>

<p>{{jsxref("double")}} 双精度浮点数。</p>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('Network Information','#dom-networkinformation-downlink','downlink')}}</td>
   <td>{{Spec2('Network Information')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_Compatibility">Browser Compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatChrome(61)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatOpera(48)}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Available in workers</td>
   <td>{{CompatChrome(61)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatOpera(48)}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android Webview</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatChrome(50)}}</td>
   <td>{{CompatChrome(38)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatOperaMobile(37)}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Available in workers</td>
   <td>{{CompatChrome(50)}}</td>
   <td>{{CompatChrome(38)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatOperaMobile(37)}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>