Revision 1023894 of PerformanceResourceTiming

<div>{{APIRef("Resource Timing API")}}</div>

<p>The <strong><code>PerformanceResourceTiming</code></strong> interface enables retrieving and analyzing detailed network timing data regarding the loading of an application's <em>resources</em>. An application can use the timing metrics to determine, for example, the length of time it takes to fetch a specific resource, such as an {{domxref("XMLHttpRequest")}}, {{SVGElement("SVG","SVG element")}}, image, or script.</p>

<p>The interface's properties create a <em>resource loading timeline</em> with {{domxref("DOMHighResTimeStamp","high-resolution timestamps")}} for network events such as redirect start and end times, fetch start, DNS lookup start and end times, response start and end times, etc. Additionally, the interface extends {{domxref("PerformanceEntry","performance entries")}} with other properties which provide data about the size of the fetched resource as well as the <em>type</em> of resource that initiated the fetch.</p>

<p>This interface extends the following {{domxref("PerformanceEntry")}} properties by qualifying and constraining these properties for {{domxref("PerformanceEntry","performance entries")}} with an {{domxref("PerformanceEntry.entryType","entry type")}} of "<code>resource</code>":</p>

<ul>
 <li>{{domxref("PerformanceEntry.entryType")}} - Set to "<code>resource</code>".</li>
 <li>{{domxref("PerformanceEntry.name")}} - Set to the resource's URL.</li>
 <li>{{domxref("PerformanceEntry.startTime")}} - Set to the {{domxref("DOMHighResTimeStamp","timestamp")}} immediately before the browser to {{domxref("PerformanceEntry.fetchStart","fetch the resource")}}.</li>
 <li>{{domxref("PerformanceEntry.duration")}} - Set to the difference between the resource's {{domxref("PerformanceResourceTiming.responseEnd","responseEnd")}} {{domxref("DOMHighResTimeStamp","timestamp")}} and its {{domxref("PerformanceEntry.startTime","startTime")}} {{domxref("DOMHighResTimeStamp","timestamp")}}.</li>
</ul>

<h2 id="Properties">Properties</h2>

<dl>
 <dt>{{domxref('PerformanceResourceTiming.initiatorType')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMString","string")}} representing the <em>type</em> of resource that initiated the performance entry, as specified in {{domxref('PerformanceResourceTiming.initiatorType')}}.</dd>
 <dt>{{domxref('PerformanceResourceTiming.nextHopProtocol')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMString","string")}} representing the <em>network protocol</em> used to fetch the resource, as identified by the <a href="https://tools.ietf.org/html/rfc7301">ALPN Protocol ID (RFC7301)</a>.</dd>
 <dt>{{domxref('PerformanceResourceTiming.workerStart')}}{{readonlyInline}}</dt>
 <dd>If the current context is a {{domxref("Worker","worker")}}, returns the {{domxref("DOMHighResTimeStamp")}} immediately before the worker is started that fetches the resource; otherwise zero is returned.</dd>
 <dt>{{domxref('PerformanceResourceTiming.redirectStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} that represents the start time of the fetch which initiates the redirect.</dd>
 <dt>{{domxref('PerformanceResourceTiming.redirectEnd')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately after receiving the last byte of the response of the last redirect.</dd>
 <dt>{{domxref('PerformanceResourceTiming.fetchStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately before the browser starts to fetch the resource.</dd>
 <dt>{{domxref('PerformanceResourceTiming.domainLookupStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately before the browser starts the domain name lookup for the resource.</dd>
 <dt>{{domxref('PerformanceResourceTiming.domainLookupEnd')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} representing the time immediately after the browser finishes the domain name lookup for the resource.</dd>
 <dt>{{domxref('PerformanceResourceTiming.connectStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately before the browser starts to establish the connection to the server to retrieve the resource.</dd>
 <dt>{{domxref('PerformanceResourceTiming.connectEnd')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately after the browser finishes establishing the connection to the server to retrieve the resource.</dd>
 <dt>{{domxref('PerformanceResourceTiming.secureConnectionStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately before the browser starts the handshake process to secure the current connection.</dd>
 <dt>{{domxref('PerformanceResourceTiming.requestStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately before the browser starts requesting the resource from the server.</dd>
 <dt>{{domxref('PerformanceResourceTiming.responseStart')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately after the browser receives the first byte of the response from the server.</dd>
 <dt>{{domxref('PerformanceResourceTiming.responseEnd')}}{{readonlyInline}}</dt>
 <dd>A {{domxref("DOMHighResTimeStamp")}} immediately after the browser receives the last byte of the resource or immediately before the transport connection is closed, whichever comes first.</dd>
 <dt>{{domxref('PerformanceResourceTiming.transferSize')}}{{readonlyInline}}</dt>
 <dd>A <code>number</code> representing the size (in octets) of the fetched resource. The size includes the response header fields plus the response payload body.</dd>
 <dt>{{domxref('PerformanceResourceTiming.encodedBodySize')}}{{readonlyInline}}</dt>
 <dd>A <code>number</code> representing the size (in octets) received from the fetch (HTTP or cahce), of the <em>payload body</em>, before removing any applied content-codings.</dd>
 <dt>{{domxref('PerformanceResourceTiming.decodedBodySize')}}{{readonlyInline}}</dt>
 <dd>A <code>number</code> that is the size (in octets) received from the fetch (HTTP or cache) of the <em>message body</em>, after removing any applied content-codings.</dd>
</dl>

<h2 id="Methods">Methods</h2>

<dl>
 <dt>{{domxref("PerformanceResourceTiming.toJSON()")}}</dt>
 <dd>Returns a {{domxref("DOMString")}} that is the JSON representation of the {{domxref("PerformanceResourceTiming")}} object.</dd>
</dl>

<h2 id="Example">Example</h2>

<p>See the example in <a href="/Web/API/Resource_Timing_API/Using_the_Resource_Timing_API">Using the Resource Timing API</a>.</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('Resource Timing', '#performanceresourcetiming', 'PerformanceResourceTiming')}}</td>
   <td>{{Spec2('Resource Timing')}}</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>43</td>
   <td>40</td>
   <td>10</td>
   <td>32</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support.</td>
   <td>4.4</td>
   <td>42</td>
   <td>{{CompatUnknown}}</td>
   <td>10.0</td>
   <td>32</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/Web/API/Resource_Timing">Resource Timing (Overview)</a></li>
 <li><a href="/Web/API/Resource_Timing_API/Using_the_Resource_Timing_API">Using the Resource Timing API</a></li>
</ul>