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<h1 class="page_title">Event Pages</h1>
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<h2>Contents</h2>
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<li>
<a href="#manifest">Manifest</a>
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<a href="#lifetime">Lifetime</a>
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<div id="static"><div id="pageData-name" class="pageData">Event Pages</div>
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<em>Warning:</em> This API is still under development. It is only
available for Chrome users on the
<span>
<strong>dev</strong>
<a href="http://www.chromium.org/getting-involved/dev-channel">early
release channel</a>.</span>
</p>
<p>
Event pages are very similar to
<a href="background_pages.html">background pages</a>,
with one important difference:
event pages are loaded only when they are needed.
When the event page is not actively doing something,
it is unloaded, freeing memory and other system resources.
</p>
<h2 id="manifest">Manifest</h2>
<p>
Register your event page in the
<a href="manifest.html">extension manifest</a>:
</p>
<pre>{
"name": "My extension",
...
<b>"background": {
"scripts": ["eventPage.js"],
"persistent": false
}</b>,
...
}</pre>
<p>
Notice that without the "persistent" key, you have
a regular background page. Persistence is what differentiates
an event page from a background page.
</p>
<h2 id="lifetime">Lifetime</h2>
<p>
The event page is loaded when it is "needed", and unloaded
when it goes idle again. Here are some examples of things
that will cause the event page to load:
</p>
<ul>
<li>The extension is first installed.
</li><li>The event page listens for an event and the event is dispatched.
</li><li>A content script or other extension
<a href="messaging.html">sends a message.</a>
</li><li>Another view in the extension (for example, a popup) calls
<code><a href="runtime.html#method-getBackgroundPage">chrome.runtime.getBackgroundPage()</a></code>.
</li></ul>
<p>
Once it has been loaded, the event page will stay running
as long as it is active (for example, calling an extension
API or issuing a network request). Additionally, the
event page will not unload until all visible views (for example,
popup windows) are closed.
</p>
<p>
Once the event page has been idle a short time
(a few seconds), the
<code><a href="runtime.html#event-onSuspend">chrome.runtime.onSuspend</a></code>
event is dispatched. The event page has a few more seconds to handle this
event before it is forcibly unloaded. Note that once the event is dispatched,
new activity will not keep the event page open.
</p>
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