path: root/chrome/common/extensions/docs/static/manifest.html

<div id="pageData-name" class="pageData">Formats: Manifest Files</div>
<div id="pageData-showTOC" class="pageData">true</div>

<p>
Every extension, installable web app, and theme has a
<a href="http://www.json.org">JSON</a>-formatted manifest file,
named <code>manifest.json</code>,
that provides important information.
</p>

<h2 id="overview"> Field summary </h2>

<p>
The following code shows the supported manifest fields,
with links to the page that discusses each field.
The only fields that are always required
are <b>name</b> and <b>version</b>.
</p>

<pre>
{
  <em>// Required</em>
  "<a href="#name">name</a>": "<em>My Extension</em>",
  "<a href="#version">version</a>": "<em>versionString</em>",

  <em>// Recommended</em>
  "<a href="#description">description</a>": "<em>A plain text description</em>",
  "<a href="#icons">icons</a>": { ... },
  "<a href="#default_locale">default_locale</a>": "<em>en</em>",

  <em>// Pick one (or none)</em>
  "<a href="browserAction.html">browser_action</a>": {...},
  "<a href="pageAction.html">page_action</a>": {...},
  "<a href="themes.html">theme</a>": {...},
  "<a href="#app">app</a>": {...},

  <em>// Add any of these that you need</em>
  "<a href="background_pages.html">background_page</a>": "<em>aFile</em>.html",
  "<a href="override.html">chrome_url_overrides</a>": {...},
  "<a href="content_scripts.html">content_scripts</a>": [...],
  "<a href="#homepage_url">homepage_url</a>": "http://<em>path/to/homepage</em>",
  "<a href="#incognito">incognito</a>": "spanning" <em>or</em> "split",
  "<a href="#key">key</a>": "<em>publicKey</em>",
  "<a href="#minimum_chrome_version">minimum_chrome_version</a>": "<em>versionString</em>",
  "<a href="omnibox.html">omnibox</a>": { "keyword" : "<em>aString</em>" },
  "<a href="options.html">options_page</a>": "<em>aFile</em>.html",
  "<a href="#permissions">permissions</a>": [...],
  "<a href="npapi.html">plugins</a>": [...],
  "<a href="autoupdate.html">update_url</a>": "http://<em>path/to/updateInfo</em>.xml"
}
</pre>


<h2>Field details</h2>

<p>
This section covers fields that aren't described in another page.
For a complete list of fields,
with links to where they're described in detail,
see the <a href="#overview">Field summary</a>.
</p>


<h3 id="app">app</h3>

<p>
Used by installable web apps,
including packaged apps,
to specify the URLs that the app uses.
Most important is the <em>launch page</em> for the app&mdash;the
page that the browser goes to when the user clicks the app's icon
in the New Tab page.
</p>

<p>
For details, see the documentation for
<a href="http://code.google.com/chrome/apps/docs/developers_guide.html">hosted apps</a> and
<a href="apps.html">packaged apps</a>.
</p>

<h3 id="default_locale">default_locale</h3>

<p>
Specifies the subdirectory of <code>_locales</code>
that contains the default strings for this extension.
This field is <b>required</b> in extensions
that have a <code>_locales</code> directory;
it <b>must be absent</b> in extensions
that have no <code>_locales</code> directory.
For details, see
<a href="i18n.html">Internationalization</a>.
</p>

<h3 id="description">description</h3>

<p>
A plain text string
(no HTML or other formatting;
no more than 132 characters)
that describes the extension.
The description should be suitable for both
the browser's extension management UI
and the <a href="https://chrome.google.com/webstore">Chrome Web Store</a>.
You can specify locale-specific strings for this field;
see <a href="i18n.html">Internationalization</a> for details.
</p>

<h3 id="homepage_url">homepage_url</h3>

<p>
The URL of the homepage for this extension. The extensions management page (chrome://extensions)
will contain a link to this URL.  This field is particularly useful if you
<a href="hosting.html">host the extension on your own site</a>. If you distribute your
extension using the <a href="https://chrome.google.com/extensions">Extensions Gallery</a> or <a href="https://chrome.google.com/webstore">Chrome Web Store</a>,
the homepage URL defaults to the extension's own page.
</p>

<h3 id="icons">icons</h3>

<p>
One or more icons that represent the extension, app, or theme.
You should always provide a 128x128 icon;
it's used during installation and by the Chrome Web Store.
Extensions should also provide a 48x48 icon,
which is used in the extensions management page
(chrome://extensions).
You can also specify a 16x16 icon to be used as the favicon
for an extension's pages.
The 16x16 icon is also displayed in the experimental extension
<a href="experimental.infobars.html">infobar</a>
feature.
</p>

<p>
Icons should generally be in PNG format,
because PNG has the best support for transparency.
They can, however, be in any format supported by WebKit,
including BMP, GIF, ICO, and JPEG.
Here's an example of specifying the icons:
</p>

<pre>
"icons": { "16": "icon16.png",
           "48": "icon48.png",
          "128": "icon128.png" },
</pre>

<p class="note">
<b>Important:</b>
Use only the documented icon sizes.
<br><br>
You might notice that Chrome sometimes resizes these icons down to smaller
sizes. For example, the install dialog might shrink the 128-pixel
icon down to 69 pixels.
<br><br>
However, the details of
Chrome's UI may change between versions, and these changes assume that
developers are using the documented sizes. If you use other sizes,
your icon may look bad in future versions of the browser.
</p>

<p>
If you upload your extension, app, or theme using the
<a href="https://chrome.google.com/webstore/developer/dashboard">Chrome Developer Dashboard</a>,
you'll need to upload additional images,
including at least one screenshot of your extension.
For more information,
see the
<a href="http://code.google.com/chrome/webstore/">Chrome Web Store
developer documentation</a>.
</p>

<h3 id="incognito">incognito</h3>

<p>
Either "spanning" or "split", to specify how this extension will
behave if allowed to run in incognito mode.
</p>

<p>
The default for extensions is "spanning", which means that the extension
will run in a single shared process.  Any events or messages from an incognito
tab will be sent to the shared process, with an <em>incognito</em> flag
indicating where it came from.
</p>

<p>
The default for installable web apps is "split",
which means that all app pages in
an incognito window will run in their own incognito process. If the app or extension contains a background page, that will also run in the incognito process.
This incognito process runs along side the regular process, but has a separate
memory-only cookie store. Each process sees events and messages only from its
own context (for example, the incognito process will see only incognito tab updates).
The processes are unable to communicate with each other.
</p>

<p>
As a rule of thumb, if your extension or app needs to load a tab in an incognito browser, use
<em>split</em> incognito behavior. If your extension or app needs to be logged
into a remote server or persist settings locally, use <em>spanning</em>
incognito behavior.
</p>

<h3 id="key">key</h3>

<p>
This value can be used to control
the unique ID of an extension, app, or theme when
it is loaded during development.
</p>

<p class="note">
<b>Note:</b> You don't usually need to
use this value. Instead, write your
code so that the key value doesn't matter
by using <a href="overview.html#relative-urls">relative paths</a>
and <a href="extension.html#method-getURL">chrome.extension.getURL()</a>.
</p>

<p>
To get a suitable key value, first
install your extension from a <code>.crx</code> file
(you may need to
<a href="https://chrome.google.com/webstore/developer/dashboard">upload your extension</a>
or <a href="packaging.html">package it manually</a>).
Then, in your
<a href="http://www.chromium.org/user-experience/user-data-directory">user
data directory</a>, look in the file
<code>Default/Extensions/<em>&lt;extensionId&gt;</em>/<em>&lt;versionString&gt;</em>/manifest.json</code>.
You will see the key value filled in there.
</p>

<h3 id="minimum_chrome_version">minimum_chrome_version</h3>

<p>
The version of Chrome that your extension, app, or theme requires, if any.
The format for this string is the same as for the
<a href="#version">version</a> field.

<h3 id="name">name</h3>

<p>
A short, plain text string
(no more than 45 characters)
that identifies the extension.
The name is used in the install dialog,
extension management UI,
and the <a href="https://chrome.google.com/webstore">store</a>.
You can specify locale-specific strings for this field;
see <a href="i18n.html">Internationalization</a> for details.
</p>

<h3 id="permissions">permissions</h3>

<p>
An array of permissions that the extension or app might use.
Each permission can be either one of a list of known strings
(such as "geolocation")
or a match pattern
that gives access to one or more hosts.
Permissions can help to limit damage
if your extension or app is attacked.
Some permissions are also displayed to users before installation,
as detailed in
<a href="permission_warnings.html">Permission Warnings</a>.
</p>

<p>
If an extension API requires you to declare a permission in the manifest,
then its documentation tells you how to do so.
For example,
the <a href="tabs.html">Tabs</a> page
shows you how to
declare the "tabs" permission.
</p>

<p>
Here's an example of the permissions part of a manifest file
for an extension:
</p>

<pre>
"permissions": [
  "tabs",
  "bookmarks",
  "http://www.blogger.com/",
  "http://*.google.com/",
  "unlimitedStorage"
],
</pre>

<p>
The following table lists the permissions an extension
or packaged app can use.
</p>

<p class="note">
<strong>Note:</strong>
Hosted apps can use the
"background", "geolocation", "notifications", and "unlimitedStorage" permissions,
but not any other permissions listed in this table.
</p>

<table>
<tr>
  <th> Permission </th> <th> Description </th>
</tr>
<tr>
  <td> <em>match pattern</em> </td>
  <td> Specifies a <em>host permission</em>.
       Required if the extension wants to interact
       with the code running on pages.
       Many extension capabilities, such as
       <a href="xhr.html">cross-origin XMLHttpRequests</a>,
       <a href="content_scripts.html#pi">programmatically injected
       content scripts</a>, and <a href="cookies.html">the cookies API</a>
       require host permissions. For details on the syntax, see
       <a href="match_patterns.html">Match Patterns</a>.
  </td>
</tr>
<tr>
  <td> "background" </td>
  <td> <p>
       Makes Chrome start up early and and shut down late,
       so that apps and extensions can have a longer life.
       </p>

       <p>
       When any installed hosted app, packaged app, or extension
       has "background" permission, Chrome runs (invisibly)
       as soon as the user logs into their computer&mdash;before
       the user launches Chrome.
       The "background" permission also makes Chrome continue running
       (even after its last window is closed)
       until the user explicitly quits Chrome.
       </p>

       <p class="note">
       <b>Note:</b>
       Disabled apps and extensions
       are treated as if they aren't installed.
       </p>

       <p>
       You typically use the "background" permission with a
       <a href="background_pages.html">background page</a>
       or (for hosted apps) a
       <a href="http://code.google.com/chrome/apps/docs/background.html">background window</a>.
       </p>
       </td>
</tr>
<tr>
  <td> "bookmarks" </td>
  <td> Required if the extension uses the
       <a href="bookmarks.html">chrome.bookmarks</a> module. </td>
</tr>
<tr>
  <td> "chrome://favicon/" </td>
  <td> Required if the extension uses the
       "chrome://favicon/<em>url</em>" mechanism
       to display the favicon of a page.
       For example, to display the favicon of http://www.google.com/,
       you declare the "chrome://favicon/" permission
       and use HTML code like this:
       <pre>&lt;img src="chrome://favicon/http://www.google.com/"></pre>
       </td>
</tr>
<tr>
  <td> "contextMenus" </td>
  <td> Required if the extension uses the
       <a href="contextMenus.html">chrome.contextMenus</a> module. </td>
</tr>
<tr>
  <td> "cookies" </td>
  <td> Required if the extension uses the
       <a href="cookies.html">chrome.cookies</a> module. </td>
</tr>
<tr>
  <td> "experimental" </td>
  <td> Required if the extension uses any
       <a href="http://code.google.com/chrome/extensions/dev/experimental.html">chrome.experimental.* APIs</a>.</td>
</tr>
<tr>
  <td id="geolocation"> "geolocation" </td>
  <td> Allows the extension to use the proposed HTML5
       <a href="http://dev.w3.org/geo/api/spec-source.html">geolocation API</a>
       without prompting the user for permission. </td>
</tr>
<tr>
  <td> "history" </td>
  <td> Required if the extension uses the
       <a href="history.html">chrome.history</a> module. </td>
</tr>
<tr>
  <td> "idle" </td>
  <td> Required if the extension uses the
       <a href="idle.html">chrome.idle</a> module. </td>
</tr>
<tr>
  <td> "management" </td>
  <td> Required if the extension uses the
       <a href="management.html">chrome.management</a> module. </td>
</tr>
<tr>
  <td> "notifications" </td>
  <td> Allows the extension to use the proposed HTML5
       <a href="http://www.chromium.org/developers/design-documents/desktop-notifications/api-specification">notification API</a>
       without calling permission methods
       (such as <code>checkPermission()</code>).
       For more information see
       <a href="notifications.html">Desktop Notifications</a>.</td>
</tr>
<tr>
  <td> "tabs" </td>
  <td> Required if the extension uses the
       <a href="tabs.html">chrome.tabs</a> or
       <a href="windows.html">chrome.windows</a> module. </td>
</tr>
<tr>
  <td> "unlimitedStorage"</td>
  <td> Provides an unlimited quota for storing HTML5 client-side data,
       such as databases and local storage files. 
       Without this permission, the extension is limited to
       5 MB of local storage.

      <p class="note">
      <b>Note:</b>
      This permission applies only to Web SQL Database and application cache
      (see issue <a href="http://crbug.com/58985">58985</a>).
      Also, it doesn't currently work with wildcard subdomains such as
      <code>http://*.example.com</code>.
      </p>       
  </td>
</tr>
</table>


<h3 id="version">version</h3>

<p>
One to four dot-separated integers
identifying the version of this extension.
A couple of rules apply to the integers:
they must be between 0 and 65535, inclusive,
and non-zero integers can't start with 0.
For example, 99999 and 032 are both invalid.
</p>

<p>
Here are some examples of valid versions:
</p>

<ul>
  <li> <code>"version": "1"</code> </li>
  <li> <code>"version": "1.0"</code> </li>
  <li> <code>"version": "2.10.2"</code> </li>
  <li> <code>"version": "3.1.2.4567"</code> </li>
</ul>

<p>
The autoupdate system compares versions
to determine whether an installed extension
needs to be updated.
If the published extension has a newer version string
than the installed extension,
then the extension is automatically updated.
</p>

<p>
The comparison starts with the leftmost integers.
If those integers are equal,
the integers to the right are compared,
and so on.
For example, 1.2.0 is a newer version than 1.1.9.9999.
</p>

<p>
A missing integer is equal to zero.
For example, 1.1.9.9999 is newer than 1.1.
</p>

<p>
For more information, see
<a href="autoupdate.html">Autoupdating</a>.
</p>

<!-- [PENDING: Possibly: point to the store/dashboard and make a big deal of the fact that autoupdating is free if you use them.] -->