chrome/common/extensions/docs/static/permission_warnings.html

<div id="pageData-name" class="pageData">Permission Warnings</div>
<div id="pageData-showTOC" class="pageData">true</div>

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<p>
To use most chrome.* APIs and extension capabilities,
your extension must declare its intent in the
<a href="manifest.html">manifest</a>,
often in the "permissions" field.
Some of these declarations
result in a warning when
a user installs your extension.
</p>

<p>
When you autoupdate your extension,
the user might see another warning
if the extension requests new permissions.
These new permissions might be new APIs that your extension uses,
or they might be new websites
that your extension needs access to.
</p>


<h2 id="examples"> Examples of permission warnings </h2>

<p>
Here's a typical dialog
that a user might see when installing an extension:
</p>

<img src="images/perms-hw1.png"
  width="410" height="193"
  alt="Permission warning: 'It can access: Your data on api.flickr.com'"
  />

<p>
The warning about access to data on api.flickr.com
is caused by the following lines
in the extension's manifest:
</p>

<pre>
"permissions": [
  <b>"http://api.flickr.com/"</b>
],
</pre>

<p class="note">
<b>Note:</b>
You don't see permission warnings when
you load an unpacked extension.
You get permission warnings only when you install an extension
from a <code>.crx</code> file.
</p>

<p>
If you add a permission to the extension when you autoupdate it,
the user might see a new permission warning.
For example,
assume you add a new site and the "tabs" permission 
to the previous example:
</p>

<pre>
"permissions": [
  "http://api.flickr.com/",
  <b>"http://*.flickr.com/",
  "tabs"</b>
],
</pre>

<p>
When the extension autoupdates,
the increased permissions
cause the extension to be disabled
until the user re-enables it.
Here's the warning the user sees:
</p>

<img src="images/perms-hw2-disabled.png"
  width="814" height="30"
  alt="Warning text: 'The newest version of the extension Hello World requires more permissions, so it has been disabled. [Re-enable].'"
  />

<p>
Clicking the Re-enable button
brings up the following warning:
</p>

<img src="images/perms-hw2.png"
  width="412" height="220"
  alt="Permission warning: 'It can access: Your data on api.flickr.com and flickr.com; Your browsing history'"
  />


<h2 id="warnings"> Warnings and their triggers </h2>

<p>
It can be surprising when adding a permission such as "tabs"
results in the seemingly unrelated warning
that the extension can access your browsing history.
The reason for the warning is that
although the <code>chrome.tabs</code> API
might be used only to open new tabs,
it can also be used to see the URL that's associated
with every newly opened tab
(using their <a href="tabs.html#type-Tab">Tab</a> objects).
</p>

<p class="note">
<b>Note:</b>
As of Google Chrome 7,
you no longer need to specify the "tabs" permission
just to call <code>chrome.tabs.create()</code>
or <code>chrome.tabs.update()</code>.
</p>

<p>
The following table lists the warning messages
that users can see,
along with the manifest entries
that trigger them.
</p>

<p>
<table>
<tr>
  <th>Warning&nbsp;message</th> <th>Manifest&nbsp;entry&nbsp;that&nbsp;causes&nbsp;it</th> <th>Notes</th>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_FULL_ACCESS -->
    All data on your computer and the websites you visit
  </td>
  <td>
    "plugins"
  </td>
  <td>
    The "plugins" permission is required by
    <a href="npapi.html">NPAPI plugins</a>.
  </td>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_BOOKMARKS -->
    Your bookmarks
  </td>
  <td>
    "bookmarks" permission
  </td>
  <td>
    The "bookmarks" permission is required by the
    <a href="bookmarks.html"><code>chrome.bookmarks</code></a> module.
  </td>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_BROWSING_HISTORY -->
    Your browsing history
  </td>
  <td>
    <!-- HasEffectiveBrowsingHistoryPermission -->
     "history" or "tabs" permission
  </td>
  <td>
    <p>
      The "tabs" permission is required by the
      <a href="tabs.html"><code>chrome.tabs</code></a> and 
      <a href="windows.html"><code>chrome.windows</code></a> modules.
    </p>
    <p>
      The "history" permission is required by
      <a href="history.html"><code>chrome.history</code></a>.
    </p>
    <p>
      Adding "tabs" to an existing extension
      that already has "history", or vice versa,
      doesn't cause a warning when the extension is autoupdated.
    </p>
  </td>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_ALL_HOSTS -->
    Your data on all websites
  </td>
  <td>
    <!-- HasEffectiveAccessToAllHosts() -->
    Any of the following:
    <ul>
      <li> "proxy" permission (experimental) </li>
      <li> A match pattern in the "permissions" field
        that matches all hosts </li>
      <li> A&nbsp;"content_scripts" field with a "matches" entry
        that matches all hosts </li>
    </ul>
  </td>
  <td>
    <p>
      The "proxy" permission is required by the
      <a href="http://code.google.com/chrome/extensions/dev/experimental.proxy.html">experimental proxy</a> module.
    </p>

    <p>
      Any of the following URLs match all hosts:
    </p>
    <ul>
      <li> <code>http://*/*</code> </li>
      <li> <code>https://*/*</code> </li>
      <li> <code>*://*/*</code> </li>
      <li> <code>&lt;all_urls&gt;</code> </li>
    </ul>
  </td>
</tr>
<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_?_HOST -->
    <!-- IDS_EXTENSION_PROMPT_WARNING_4_OR_MORE_HOSTS -->
    Your data on <em>{list of websites}</em>
  </td>
  <td>
    A match pattern in the "permissions" field
    that specifies one or more hosts,
    but not all hosts
  </td>
  <td>
    <p>
    Up to 3 sites are listed by name.
    Subdomains aren't treated specially.
    For example, <code>a.com</code> and <code>b.a.com</code>
    are listed as different sites.
    </p>

    <p>
    On autoupdate,
    the user sees a permission warning
    if the extension adds or changes sites.
    For example, going from <code>a.com,b.com</code>
    to <code>a.com,b.com,c.com</code>
    triggers a warning.
    Going from <code>b.a.com</code>
    to <code>a.com</code>,
    or vice versa,
    also triggers a warning.
    </p>
  </td>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_MANAGEMENT -->
    Your list of installed apps, extensions, and themes
    <br />
    <span style="font-weight:normal; font-style:italic">or</span>
    <br />
    Manage themes, extensions, and apps

    <!-- PENDING: remove "Manage...apps" alternative message
    once the fix is out on stable channel -->
    <!-- See http://crbug.com/67859 -->
  </td>
  <td>
    "management" permission
  </td>
  <td>
    The "management" permission is required by the
    <a href="management.html"><code>chrome.management</code></a> module.
  </td>
</tr>

<tr>
  <td style="font-weight:bold">
    <!-- IDS_EXTENSION_PROMPT_WARNING_GEOLOCATION -->
    Your physical location
  </td>
  <td>
    "geolocation" permission
  </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>
</table>
</p>


<h2 id="nowarning"> Permissions that don't cause warnings </h2>

<p>
The following permissions don't result in a warning:
</p>

<ul>
  <li>"chrome://favicon/"</li>
  <li>"contextMenus"</li>
  <li>"cookies"</li>
  <li>"experimental"</li>
  <li>"idle"</li>
  <li>"notifications"</li>
  <li>"unlimitedStorage"</li>
</ul>

<h2 id="test"> Testing permission warnings </h2>

<p>
If you'd like to see exactly which warnings your users will get,
<a href="packaging.html">package your extension</a>
into a <code>.crx</code> file,
and install it.
</p>

<p>
To see the warnings users will get when your extension is autoupdated,
you can go to a little more trouble
and set up an autoupdate server.
To do this, first create an update manifest
and point to it from your extension,
using the "update_url" key
(see <a href="autoupdate.html">Autoupdating</a>).
Next, <a href="packaging.html">package the extension</a>
into a new <code>.crx</code> file,
and install the app from this <code>.crx</code> file.
Now, change the extension's manifest to contain the new permissions,
and <a href="packaging.html#update">repackage the extension</a>.
Finally, update the extension
(and all other extensions that have outstanding updates)
by clicking the <b>chrome://extensions</b> page's
<b>Update extensions now</b> button.
</p>