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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>
Navigation Timing Level 2
</title>
<style>
#obsolete {
background-position: right;
background-repeat: repeat-y;
background-color: rgba(251, 233, 233, 0.5);
padding: 0 1em;
background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' version='1.1' height='300px' width='125px'><text x='0' y='100' fill='red' font-size='15' fill-opacity='0.20'>Obsolete<\/text><\/svg>")
}
</style>
<script src='https://www.w3.org/Tools/respec/respec-w3c' class='remove' defer></script>
<script class='remove'>
var respecConfig = {
shortName: "navigation-timing-2",
specStatus: "ED",
editors: [{
name: "Yoav Weiss",
url: "https://blog.yoav.ws/",
mailto: "yoav@yoav.ws",
company: "Google",
companyURL: "https://google.com/",
w3cid: "58673"
}, {
name: "Noam Rosenthal",
mailto: "noam.j.rosenthal@gmail.com",
company: "Invited Expert",
w3cid: "121539"
}],
formerEditors: [
{
name: "Ilya Grigorik",
url: "https://www.igvita.com/",
mailto: "igrigorik@gmail.com",
company: "Google",
companyURL: "https://www.google.com/",
w3cid: "56102",
},
{
name: "Tobin Titus",
mailto: "tobint@microsoft.com",
retiredDate: "2015-01-01",
company: "Microsoft Corp.",
w3cid: "69474",
},
{
name: "Jatinder Mann",
mailto: "jmann@microsoft.com",
company: "Microsoft Corp.",
retiredDate: "2014-02-01",
w3cid: "44357",
},
{
name: "Arvind Jain",
mailto: "arvind@google.com",
company: "Google Inc.",
retiredDate: "2014-12-01",
w3cid: "45188",
},
],
group:"webperf",
wgPublicList: "public-web-perf",
subjectPrefix: "[NavigationTiming]",
github: "https://github.com/w3c/navigation-timing/",
testSuiteURI: "https://wpt.fyi/navigation-timing/",
caniuse: "nav-timing",
mdn: "navigation-timing",
xref: {
url: "https://respec.org/xref",
specs: [ "service-workers", "hr-time-2", "performance-timeline-2", "resource-timing-2", "html", "fetch"],
profile: "web-platform",
},
localBiblio: {
JSMEASURE: {
title: "Measuring Client-Perceived Response Times on the WWW",
href:
"http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.69.7329&rep=rep1&type=pdf",
authors: ["Ramakrishnan Rajamony", "Mootaz Elnozahy"],
status:
"The Proceedings of the 3rd USENIX Symposium on Internet Technologies and Systems (USITS)",
date: "March 2001",
},
},
lint: {
"check-punctuation": true,
},
doJsonLd: true,
};
</script>
</head>
<body>
<section id="abstract">
<p>
This specification defines an interface for web applications to access
the complete timing information for navigation of a document.
</p>
</section>
<section id="sotd">
<p>
Navigation Timing 2 replaces the first version of [[NAVIGATION-TIMING]]
and includes the following changes:
</p>
<ul>
<li>the definition of Performance interface was moved to
[[PERFORMANCE-TIMELINE-2]];
</li>
<li>builds on top of [[RESOURCE-TIMING-2]];
</li>
<li>support for [[PERFORMANCE-TIMELINE-2]];
</li>
<li>support for [[HR-TIME-2]];
</li>
<li>support for <a data-cite="resource-hints#prerender">prerender</a>
navigations [[RESOURCE-HINTS]];
</li>
<li>exposes <a data-lt=
'PerformanceNavigationTiming.redirectCount'>number of redirects</a>
since the last non-redirect navigation;
</li>
<li>exposes <a data-cite=
'resource-timing-2#dom-performanceresourcetiming-nexthopprotocol'>next
hop network protocol</a>;
</li>
<li>exposes <a data-cite=
'resource-timing-2#dom-performanceresourcetiming-transfersize'>transfer</a>,
<a data-cite=
'resource-timing-2#dom-performanceresourcetiming-encodedbodysize'>encoded
body</a> and <a data-cite=
'resource-timing-2#dom-performanceresourcetiming-decodedbodysize'>decoded
body</a> size information;
</li>
<li>
<a data-cite=
'resource-timing-2#dom-performanceresourcetiming-secureconnectionstart'>
secureConnectionStart</a> attribute is now mandatory.
</li>
</ul>
</section>
<section id="introduction" class='informative'>
<h2>
Introduction
</h2>
<p>
Accurately measuring performance characteristics of web applications is
an important aspect of making web applications faster. While
JavaScript-based mechanisms, such as the one described in
[[JSMEASURE]], can provide comprehensive instrumentation for user
latency measurements within an application, in many cases, they are
unable to provide a complete or detailed end-to-end latency picture.
For example, the following JavaScript shows a naive attempt to measure
the time it takes to fully load a page:
</p>
<pre class='example'>
<html>
<head>
<script type="text/javascript">
var start = new Date().getTime();
function onLoad() {
var now = new Date().getTime();
var latency = now - start;
alert("page loading time: " + latency);
}
</script>
</head>
<body onload="onLoad()">
<!- Main page body goes from here. -->
</body>
</html>
</pre>
<p>
The above script calculates the time it takes to load the page
<b>after</b> the first bit of JavaScript in the head is executed, but
it does not give any information about the time it takes to get the
page from the server, or the initialization lifecycle of the page.
</p>
<p>
This specification defines the {{PerformanceNavigationTiming}}
interface which participates in the [[PERFORMANCE-TIMELINE-2]] to store
and retrieve high resolution performance metric data related to the
navigation of a document. As the {{PerformanceNavigationTiming}}
interface uses [[HR-TIME-2]], all time values are measured with respect
to the <a data-cite="HR-TIME-2#dfn-time-origin">time origin</a> of the
{{Window}} object.
</p>
<p>
For example, if we know that the response end occurs 100ms after the
start of navigation, the {{PerformanceNavigationTiming}} data could
look like so:
</p>
<pre class="example">
startTime: 0.000 // start time of the navigation request
responseEnd: 100.000 // high resolution time of last received byte
</pre>
<p>
The following script shows how a developer can use the
{{PerformanceNavigationTiming}} interface to obtain accurate timing
data related to the navigation of the document:
</p>
<pre class="example">
<script>
function showNavigationDetails() {
// Get the first entry
const [entry] = performance.getEntriesByType("navigation");
// Show it in a nice table in the developer console
console.table(entry.toJSON());
}
</script>
<body onload="showNavigationDetails()">
</pre>
</section>
<section id="terminology">
<h2>
Terminology
</h2>
<p>
The construction "a <code>Foo</code> object", where <code>Foo</code> is
actually an interface, is sometimes used instead of the more accurate
"an object implementing the interface <code>Foo</code>.
</p>
<p>
The term <dfn>navigation</dfn> refers to the act of <a data-lt=
"navigate">navigating</a>.
</p>
<p>
The term <dfn>current document</dfn> refers to the document associated
with the <a data-lt="associated document">Window object's newest
Document object</a>.
</p>
<p>
The term <dfn>JavaScript</dfn> is used to refer to ECMA262, rather than
the official term ECMAScript, since the term JavaScript is more widely
known. [[ECMASCRIPT]]
</p>
<p>
Throughout this work, all time values are measured in milliseconds
since the start of navigation of the document. For example, the start
of navigation of the document occurs at time 0. The term <i>current
time</i> refers to the number of milliseconds since the start of
navigation of the document until the current moment in time. This
definition of time is based on [[HR-TIME-2]] specification.
</p>
</section>
<section id="sec-navigation-timing">
<h2>
Navigation Timing
</h2>
<section id='performanceentry'>
<h3>
Relation to the {{PerformanceEntry}} interface
</h3>
<p>
{{PerformanceNavigationTiming}} interface extends the following
attributes of <code><dfn data-cite=
"PERFORMANCE-TIMELINE-2#dom-performanceentry">PerformanceEntry</dfn></code>
interface:
</p>
<ul>
<li>The <dfn id=
'dom-PerformanceNavigationTiming-name'><code>name</code></dfn>
attribute MUST return the {{DOMString}} value of the <a data-cite=
"HTML#the-document's-address">address</a> of the <a>current
document</a>.
</li>
<li>The <dfn id=
'dom-PerformanceNavigationTiming-entryType'><code>entryType</code></dfn>
attribute MUST return the {{DOMString}} "<code id=
"perf-navigation">navigation</code>".
</li>
<li>The <dfn id=
'dom-PerformanceNavigationTiming-startTime'><code>startTime</code></dfn>
attribute MUST return a <code><dfn data-cite=
"HR-TIME-2#dom-domhighrestimestamp">DOMHighResTimeStamp</dfn></code>
with a time value of 0. [[HR-TIME-2]]
</li>
<li>The <dfn id=
'dom-PerformanceNavigationTiming-duration'><code>duration</code></dfn>
attribute MUST return a {{DOMHighResTimeStamp}} equal to the
difference between <a data-link-for=
"PerformanceNavigationTiming">loadEventEnd</a> and {{startTime}},
respectively.
</li>
</ul>
<p class="note">
A user agent implementing {{PerformanceNavigationTiming}} would need
to include <code>"navigation"</code> in <a data-cite=
"PERFORMANCE-TIMELINE-2#supportedentrytypes-attribute">supportedEntryTypes</a>
for <a data-cite="HTML/window-object.html#window">Window</a>
contexts. This allows developers to detect support for Navigation
Timing.
</p>
</section>
<section id='PerformanceResourceTiming'>
<h3>
Relation to the <code>PerformanceResourceTiming</code> interface
</h3>
<p>
{{PerformanceNavigationTiming}} interface extends the following
attributes of the <code><dfn data-cite=
"RESOURCE-TIMING-2#dom-performanceresourcetiming">PerformanceResourceTiming</dfn></code>
interface:
</p>
<ul>
<li>The `workerStart` getter steps are to perform the following steps:
<ol>
<li>Let |workerTiming| be |this|'s [=PerformanceNavigationTiming/service worker timing=].
<li>If |workerTiming| is null, then return |this|'s prototype's `workerStart`.
<li>Return |workerTiming|'s [=service worker timing info/start time=].
</ol>
</li>
<li>The `fetchStart` getter steps are to perform the following steps:
<ol>
<li>Let |workerTiming| be |this|'s [=PerformanceNavigationTiming/service worker timing=].
<li>If |workerTiming| is null, then return |this|'s prototype's `fetchStart`.
<li>Return |workerTiming|'s [=service worker timing info/fetch event dispatch time=].
</ol>
</li>
</ul>
<p class="note">
Only the <a>current document</a> resource is included in the
performance timeline; there is only one
{{PerformanceNavigationTiming}} object in the performance timeline.
</p>
</section>
<section data-dfn-for="PerformanceNavigationTiming" id=
"sec-PerformanceNavigationTiming">
<h3>
The <dfn>PerformanceNavigationTiming</dfn> interface
</h3><!-- from domainLookupEnd -->
<div class="note">
<p>
Checking and retrieving contents from the <a href=
"https://tools.ietf.org/html/rfc7234">HTTP cache</a> [[RFC7234]] is
part of the <a data-cite="FETCH#concept-fetch" title=
'fetch'>fetching process</a>. It's covered by the <a data-cite=
"resource-timing-2#dom-performanceresourcetiming-requeststart"><code>
requestStart</code></a>, <a data-cite=
"resource-timing-2#dom-performanceresourcetiming-responsestart"><code>
responseStart</code></a> and <a data-cite=
"resource-timing-2#dom-performanceresourcetiming-responseend"><code>
responseEnd</code></a> attributes.
</p>
</div>
<pre class='idl'>
[Exposed=Window]
interface PerformanceNavigationTiming : PerformanceResourceTiming {
readonly attribute DOMHighResTimeStamp unloadEventStart;
readonly attribute DOMHighResTimeStamp unloadEventEnd;
readonly attribute DOMHighResTimeStamp domInteractive;
readonly attribute DOMHighResTimeStamp domContentLoadedEventStart;
readonly attribute DOMHighResTimeStamp domContentLoadedEventEnd;
readonly attribute DOMHighResTimeStamp domComplete;
readonly attribute DOMHighResTimeStamp loadEventStart;
readonly attribute DOMHighResTimeStamp loadEventEnd;
readonly attribute NavigationType type;
readonly attribute unsigned short redirectCount;
[Default] object toJSON();
};
</pre>
<p>A <a>PerformanceNavigationTiming</a> has an associated
[=document load timing info=] <a data-dfn-for="PerformanceResourceTiming">
<dfn>document load timing</dfn></a>.
<p>A <a>PerformanceNavigationTiming</a> has an associated
[=document unload timing info=] <a data-dfn-for="PerformanceNavigationTiming">
<dfn>previous document unload timing</dfn></a>.
<p>A <a>PerformanceNavigationTiming</a> has an associated
number <a data-dfn-for="PerformanceNavigationTiming"><dfn>redirect count</dfn></a>.
<p>A <a>PerformanceNavigationTiming</a> has an associated
{{NavigationType}} <a data-dfn-for="PerformanceNavigationTiming"><dfn>navigation type</dfn></a>.
<p>A {{PerformanceNavigationTiming}} has an associated null or [=service worker timing info=]
<dfn data-dfn-for="PerformanceNavigationTiming">service worker timing</dfn>.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>unloadEventStart</dfn> getter steps are to return |this|'s
[=previous document unload timing=]'s [=document unload timing info/unload event start time=].
</li>
<p class="note">See <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload event</a> for more info.</p>
</ol>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>unloadEventEnd</dfn> getter steps are to return |this|'s
[=previous document unload timing=]'s [=document unload timing info/unload event end time=].</li>
<p class="note">See <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload event</a> for more info.</p>
</ol>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domInteractive</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/DOM interactive time=].</p>
<p class="note">See <a data-cite=
"HTML/dom.html#current-document-readiness">document readiness</a> for more info.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domContentLoadedEventStart</dfn> getter steps are to return |this|'s
[=document load timing=]'s
[=document load timing info/DOM content loaded event start time=].</p>
<p class="note">See <a data-cite=
"HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded</a> for more info.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domContentLoadedEventEnd</dfn> getter steps are to return
|this|'s [=document load timing=]'s
[=document load timing info/DOM content loaded event end time=].</p>
<p class="note">See <a data-cite=
"HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded
event</a> completes.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domComplete</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/DOM complete time=].
<p class="note">See <a data-cite=
"HTML/dom.html#current-document-readiness">document readiness</a> for more info.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>loadEventStart</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/load event start time=].</p>
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>loadEventEnd</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/load event end time=].</p>
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>type</dfn> getter steps are to run the |this|'s [=navigation type=].
</p>
<div class="note">
<p>
Client-side redirects, such as those using the <a data-cite=
"HTML/semantics.html#attr-meta-http-equiv-refresh">Refresh pragma
directive</a>, are not considered <a data-cite=
"FETCH#redirect-status">HTTP redirects</a> by this spec. In those
cases, the <a data-link-for="PerformanceNavigationTiming">type</a>
attribute SHOULD return appropriate value, such as
<a data-link-for="NavigationType">reload</a> if reloading the
current page, or <a data-link-for="NavigationType">navigate</a> if
navigating to a new URL.
</p>
</div>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>redirectCount</dfn> getter steps are to return |this|'s
<span>redirect count</span>.</p>
</p>
<p>
The <dfn>toJSON()</dfn> method runs [WEBIDL]'s <a data-cite=
"WEBIDL/#default-tojson-operation">default toJSON operation</a>.
</p>
<section id="sec-performance-navigation-types">
<h4>
<dfn>NavigationType</dfn> enum
</h4>
<pre class='idl'>
enum NavigationType {
"navigate",
"reload",
"back_forward",
"prerender"
};
</pre>
<p>
The values are defined as follows:
</p>
<dl data-dfn-for='NavigationType'>
<dt>
<dfn>navigate</dfn>
</dt>
<dd>
Navigation where the
<a data-cite="HTML/browsing-the-web.html#history-handling-behavior">history handling behavior</a>
is set to
<a data-cite="HTML/browsing-the-web.html#hh-default">"default"</a>
or <a data-cite="HTML/browsing-the-web.html#hh-replace">"replace"</a>
and the navigation was not initiated by a <a data-cite=
'resource-hints#prerender'>prerender</a> hint [[RESOURCE-HINTS]].
</dd>
<dt>
<dfn>reload</dfn>
</dt>
<dd>
Navigation where the
<a data-cite="HTML/browsing-the-web.html#history-handling-behavior">history handling behavior</a>
is set to
<a data-cite="HTML/browsing-the-web.html#hh-reload">"reload"</a>.
</dd>
<dt>
<dfn>back_forward</dfn>
</dt>
<dd>
Navigation where the
<a data-cite="HTML/browsing-the-web.html#history-handling-behavior">history handling behavior</a>
is set to
<a data-cite="HTML/browsing-the-web.html#hh-entry-update">"entry update"</a>.
</dd>
<dt>
<dfn>prerender</dfn>
</dt>
<dd>
Navigation initiated by a <a data-cite=
'resource-hints#prerender'>prerender</a> hint [[RESOURCE-HINTS]].
</dd>
</dl>
<p class="note">
The format of the above enumeration value is inconsistent with the
<a data-cite="WEBIDL/#idl-enums">WebIDL recommendation for
formatting of enumeration values</a>. Unfortunately, we are unable
to change it due to backwards compatibility issues with shipped
implementations.
</p>
</section>
</section>
</section>
<section id="process">
<h2>
Process
</h2>
<section id="processing-model">
<h3>
Processing Model
</h3>
<figure title='Timing attributes'>
<figcaption>
This figure illustrates the timing attributes defined by the
{{PerformanceNavigationTiming}} interface. Attributes in
parenthesis indicate that they may not be available for navigations
involving documents from different <a data-cite=
"html#concept-origin" title='origin'>origins</a>.
</figcaption>
<!-- Source: https://docs.google.com/document/d/1I7XGNJ57Qgjkg9pL11s7MK7zGEcwAgdNj1W5f7NKbW8/ -->
<img src="timestamp-diagram.svg" alt="Navigation Timing attributes"
style='width: 100%'>
</figure>
</section>
</section>
<section id="marking-navigation-timing">
<h2>Creating a navigation timing entry</h2>
<p data-dfn-for="Document">Each [=document=] has an associated <dfn>navigation timing entry</dfn>, initially unset.
<p>To <dfn export="">create the navigation timing entry</dfn> for {{Document}} |document|,
given a [=fetch timing info=] |fetchTiming|, a number |redirectCount|, a
{{NavigationType}} |navigationType|, and a null or [=service worker timing info=] |serviceWorkerTiming|,
do the following:
<ol>
<li>Let |global| be |document|'s [=relevant global object=].</li>
<li>Let |navigationTimingEntry| be a new {{PerformanceNavigationTiming}} object in |global|'s
[=global object/realm=].
<li><a data-cite="RESOURCE-TIMING-2#dfn-setup-the-resource-timing-entry">Setup the resource
timing entry</a> for |navigationTimingEntry| given "<code>navigation</code>", |document|'s
<a data-cite="HTML#the-document's-address">address</a>, and |fetchTiming|.
<li>Set |navigationTimingEntry|'s <a data-for="PerformanceNavigationTiming">document load
timing</a> to |document|'s [=Document/load timing info=]
<li>Set |navigationTimingEntry|'s <a data-for="PerformanceNavigationTiming">previous
document unload timing</a> to |document|'s [=Document/previous document unload timing=].
<li>Set |navigationTimingEntry|'s <a data-for="PerformanceNavigationTiming">redirect
count</a> to |redirectCount|.
<li>Set |navigationTimingEntry|'s <a data-for="PerformanceNavigationTiming">navigation
type</a> to |navigationType|.
<li>Set |navigationTimingEntry|'s [=PerformanceNavigationTiming/service worker timing=]
to |serviceWorkerTiming|.
<li>Set |document|'s <span>navigation timing entry</span> to |navigationTimingEntry|.
<li>add |navigationTimingEntry| to |global|'s
<a data-cite='performance-timeline-2#dfn-performance-entry-buffer'>performance entry buffer</a>.
</ol>
<p>To <dfn export="">queue the navigation timing entry</dfn> for {{Document}} |document|,
<a data-cite='performance-timeline-2#dfn-queue-a-performanceentry'>queue</a> |document|'s
<span>navigation timing entry</span>.
</secript>
<section id="privacy" class='informative'>
<h2>
Privacy
</h2>
<section id="info_disclosure">
<h3>
Information disclosure
</h3>
<p>
There is the potential for disclosing an end-user's browsing and
activity history by using carefully crafted timing attacks. For
instance, the unloading time reveals how long the previous page takes
to execute its unload handler, which could be used to infer the
user's login status. These attacks have been mitigated by enforcing
the [=same origin=] check algorithm when unloading a document, as detailed in
<a data-cite="HTML#update-the-session-history-with-the-new-page">the HTML spec</a>.
</p>
<p>
The <a data-cite=
"HTML/origin.html#relaxing-the-same-origin-restriction">relaxed same
origin policy</a> doesn't provide sufficient protection against
unauthorized visits across documents. In shared hosting, an untrusted
third party is able to host an HTTP server at the same IP address but
on a different port.
</p>
</section>
<section id="cross-directory">
<h3>
Cross-directory access
</h3>
<p>
Different pages sharing one host name, for example contents from
different authors hosted on sites with user generated content are
considered from the same origin because there is no feature to
restrict the access by pathname. Navigating between these pages
allows a latter page to access timing information of the previous
one, such as timing regarding redirection and unload event.
</p>
</section>
</section>
<section id="security" class='informative'>
<h2>
Security
</h2>
<p>
The {{PerformanceNavigationTiming}} interface exposes timing
information about the previous document to the <a>current document</a>.
To limit the access to {{PerformanceNavigationTiming}} attributes which
include information on the previous document, the
<a data-cite="HTML#update-the-session-history-with-the-new-page">previous document
unloading</a> algorithm enforces the <a data-cite="html#same-origin">same origin policy</a>
and attributes related to the previous document are set to zero.
</p>
<section id="authentication">
<h3>
Detecting proxy servers
</h3>
<p>
In case a proxy is deployed between the user agent and the web
server, the time interval between the <a data-cite=
"resource-timing-2#dom-performanceresourcetiming-connectstart"><code>connectStart</code></a>
and the <a data-cite=
"resource-timing-2#dom-performanceresourcetiming-connectend"><code>connectEnd</code></a>
attributes indicates the delay between the user agent and the proxy
instead of the web server. With that, web server can potentially
infer the existence of the proxy. For SOCKS proxy, this time interval
includes the proxy authentication time and time the proxy takes to
connect to the web server, which obfuscate the proxy detection. In
case of an HTTP proxy, the user agent might not have any knowledge
about the proxy server at all so it's not always feasible to mitigate
this attack.
</p>
</section>
</section>
<section id='obsolete'>
<h2>
Obsolete
</h2>
<p>
This section defines attributes and interfaces previously introduced in
[[NAVIGATION-TIMING]] Level 1 and are kept here for backwards
compatibility. Authors should not use the following interfaces and are
<strong>strongly advised</strong> to use the new
{{PerformanceNavigationTiming}} interface—see <a href="#sotd">summary
of changes and improvements</a>.
</p>
<section data-dfn-for="PerformanceTiming">
<h3>
The <dfn>PerformanceTiming</dfn> interface
</h3>
<pre class="idl">
[Exposed=Window]
interface PerformanceTiming {
readonly attribute unsigned long long navigationStart;
readonly attribute unsigned long long unloadEventStart;
readonly attribute unsigned long long unloadEventEnd;
readonly attribute unsigned long long redirectStart;
readonly attribute unsigned long long redirectEnd;
readonly attribute unsigned long long fetchStart;
readonly attribute unsigned long long domainLookupStart;
readonly attribute unsigned long long domainLookupEnd;
readonly attribute unsigned long long connectStart;
readonly attribute unsigned long long connectEnd;
readonly attribute unsigned long long secureConnectionStart;
readonly attribute unsigned long long requestStart;
readonly attribute unsigned long long responseStart;
readonly attribute unsigned long long responseEnd;
readonly attribute unsigned long long domLoading;
readonly attribute unsigned long long domInteractive;
readonly attribute unsigned long long domContentLoadedEventStart;
readonly attribute unsigned long long domContentLoadedEventEnd;
readonly attribute unsigned long long domComplete;
readonly attribute unsigned long long loadEventStart;
readonly attribute unsigned long long loadEventEnd;
[Default] object toJSON();
};
</pre>
<p class="note">
All time values defined in this section are measured in milliseconds
since midnight of <time datetime="1970-01-01T00:00Z">January 1, 1970
(UTC)</time>.
</p>
<dl>
<dt>
<dfn>navigationStart</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately after the user
agent finishes <a data-cite=
"HTML/browsing-the-web.html#prompt-to-unload-a-document">prompting
to unload</a> the previous document. If there is no previous
document, this attribute must return the time the current
document is created.
</p>
<p class="note">
This attribute is not defined for
{{PerformanceNavigationTiming}}. Instead, authors can use
<a data-cite=
"HR-TIME-2#dom-performance-timeorigin">timeOrigin</a> to obtain
an equivalent timestamp.
</p>
</dd>
<dt>
<dfn>unloadEventStart</dfn>
</dt>
<dd>
<p>
If the previous document and the current document have the same
<a data-cite="html#concept-origin">origin</a>, this attribute
must return the time immediately before the user agent starts the
<a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload</a> event
of the previous document. If there is no previous document or the
previous document has a different <a data-cite=
"html#concept-origin">origin</a> than the current document, this
attribute must return zero.
</p>
</dd>
<dt>
<dfn>unloadEventEnd</dfn>
</dt>
<dd>
<p>
If the previous document and the current document have the same
<a data-cite="html#same-origin">same origin</a>, this attribute
must return the time immediately after the user agent finishes
the <a data-cite=
"HTML/browsing-the-web.html#unload-a-document">unload</a> event
of the previous document. If there is no previous document or the
previous document has a different <a data-cite=
"html#concept-origin">origin</a> than the current document or the
unload is not yet completed, this attribute must return zero.
</p>
<p>
If there are <a data-cite="FETCH#redirect-status">HTTP
redirects</a> when navigating and not all the redirects are from
the same <a data-cite="html#concept-origin">origin</a>, both
{{PerformanceTiming.unloadEventStart}} and
{{PerformanceTiming.unloadEventEnd}} must return zero.
</p>
</dd>
<dt>
<dfn>redirectStart</dfn>
</dt>
<dd>
<p>
If there are <a data-cite="FETCH#redirect-status">HTTP
redirects</a> when navigating and if all the redirects are from
the same <a data-cite="html#concept-origin">origin</a>, this
attribute must return the <a data-lt=
'PerformanceTiming.fetchStart'>starting time of the fetch</a>
that initiates the redirect. Otherwise, this attribute must
return zero.
</p>
</dd>
<dt>
<dfn>redirectEnd</dfn>
</dt>
<dd>
<p>
If there are <a data-cite="FETCH#redirect-status">HTTP
redirects</a> when navigating and all redirects are from the same
<a data-cite="html#concept-origin">origin</a>, this attribute
must return the time immediately after receiving the last byte of
the response of the last redirect. Otherwise, this attribute must
return zero.
</p>
</dd>
<dt>
<dfn>fetchStart</dfn>
</dt>
<dd>
<p>
If the new resource is to be <a data-cite=
"HTML/urls-and-fetching.html#fetching-resources">fetched</a>
using a "GET" <a data-cite="FETCH#concept-request-method">request
method</a>, fetchStart must return the time immediately before
the user agent starts checking <a data-cite=
"HTML/offline.html#relevant-application-cache">any relevant
application caches</a>. Otherwise, it must return the time when
the user agent starts <a data-cite=
"HTML/urls-and-fetching.html#fetching-resources">fetching</a> the
resource.
</p>
</dd>
<dt>
<dfn>domainLookupStart</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately before the user
agent starts the domain name lookup for the current document. If
a <a href=
"https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1">persistent
connection</a> [[RFC2616]] is used or the current document is
retrieved from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or local resources, this attribute must
return the same value as {{PerformanceTiming.fetchStart}}.
</p>
</dd>
<dt>
<dfn>domainLookupEnd</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately after the user
agent finishes the domain name lookup for the current document.
If a <a href=
"https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1">persistent
connection</a> [[RFC2616]] is used or the current document is
retrieved from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or local resources, this attribute must
return the same value as {{PerformanceTiming.fetchStart}}.
</p>
<div class="note">
<p>
Checking and retrieving contents from the <a href=
"https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13">
HTTP cache</a> [[RFC2616]] is part of the <a data-cite=
"HTML/urls-and-fetching.html#fetching-resources">fetching
process</a>. It's covered by the
{{PerformanceTiming.requestStart}},
{{PerformanceTiming.responseStart}} and
{{PerformanceTiming.responseEnd}} attributes.
</p>
</div>
<p class="note">
In case where the user agent already has the domain information
in cache, domainLookupStart and domainLookupEnd represent the
times when the user agent starts and ends the domain data
retrieval from the cache.
</p>
</dd>
<dt>
<dfn>connectStart</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately before the user
agent start establishing the connection to the server to retrieve
the document. If a <a href=
"https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1">persistent
connection</a> [[RFC2616]] is used or the current document is
retrieved from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or local resources, this attribute must
return value of {{PerformanceTiming.domainLookupEnd}}.
</p>
</dd>
<dt>
<dfn>connectEnd</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately after the user
agent finishes establishing the connection to the server to
retrieve the current document. If a <a href=
"https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1">persistent
connection</a> [[RFC2616]] is used or the current document is
retrieved from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or local resources, this attribute must
return the value of {{PerformanceTiming.domainLookupEnd}}.
</p>
<p>
If the transport connection fails and the user agent reopens a
connection, {{PerformanceTiming.connectStart}} and
{{PerformanceTiming.connectEnd}} should return the corresponding
values of the new connection.
</p>
<p>
{{PerformanceTiming.connectEnd}} must include the time interval
to establish the transport connection as well as other time
interval such as SSL handshake and SOCKS authentication.
</p>
</dd>
<dt>
<dfn>secureConnectionStart</dfn>
</dt>
<dd>
<p>
This attribute is optional. User agents that don't have this
attribute available must set it as undefined. When this attribute
is available, if the <a data-cite=
"url#concept-url-scheme">scheme</a> [[URL]] of the current page
is "https", this attribute must return the time immediately
before the user agent starts the handshake process to secure the
current connection. If this attribute is available but HTTPS is
not used, this attribute must return zero.
</p>
</dd>
<dt>
<dfn>requestStart</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately before the user
agent starts requesting the current document from the server, or
from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or from local resources.
</p>
<p>
If the transport connection fails after a request is sent and the
user agent reopens a connection and resend the request,
{{PerformanceTiming.requestStart}} should return the
corresponding values of the new request.
</p>
<div class="note">
<p>
This interface does not include an attribute to represent the
completion of sending the request, e.g., requestEnd.
</p>
<ul>
<li>Completion of sending the request from the user agent does
not always indicate the corresponding completion time in the
network transport, which brings most of the benefit of having
such an attribute.
</li>
<li>Some user agents have high cost to determine the actual
completion time of sending the request due to the HTTP layer
encapsulation.
</li>
</ul>
</div>
</dd>
<dt>
<dfn>responseStart</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately after the user
agent receives the first byte of the response from the server, or
from <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or from local resources.
</p>
</dd>
<dt>
<dfn>responseEnd</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately after the user
agent receives the last byte of the current document or
immediately before the transport connection is closed, whichever
comes first. The document here can be received either from the
server, <a data-cite=
"HTML/offline.html#relevant-application-cache">relevant
application caches</a> or from local resources.
</p>
</dd>
<dt>
<dfn>domLoading</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately before the user
agent sets the <a data-cite=
"HTML/dom.html#current-document-readiness">current document
readiness</a> to <a data-cite=
"HTML/dom.html#current-document-readiness">"loading"</a>.
</p>
<p class="warning">
Due to differences in when a Document object is created in
existing user agents, the value returned by the
<code>domLoading</code> is implementation specific and should not
be used in meaningful metrics.
</p>
</dd>
<dt>
<dfn>domInteractive</dfn>
</dt>
<dd>
<p>
This attribute must return the time immediately before the user
agent sets the <a data-cite=
"HTML/dom.html#current-document-readiness">current document
readiness</a> to <a data-cite=
"HTML/parsing.html#the-end">"interactive"</a>.