permissions

Type Array
Mandatory No
Manifest version 2 or higher
Example
json
"permissions": [
  "webRequest"
]

Use the permissions key to request special powers for your extension. This key is an array of strings, and each string is a request for a permission.

If you request permissions using this key, then the browser may inform the user at install time that the extension is requesting certain privileges, and ask them to confirm that they are happy to grant these privileges. The browser may also allow the user to inspect an extension's privileges after installation. As the request to grant privileges may impact on users' willingness to install your extension, requesting privileges is worth careful consideration. For example, you want to avoid requesting unnecessary permissions and may want to provide information about why you are requesting permissions in your extension's store description. More information on the issues you should consider is provided in the article Request the right permissions.

For information on how to test and preview permission requests, see Test permission requests on the Extension Workshop site.

The key can contain three kinds of permissions:

  • host permissions (Manifest V2 only, host permissions are specified in the host_permissions manifest key for Manifest V3 or higher.)
  • API permissions
  • the activeTab permission

Host permissions

Note: How you request host permissions depends on whether you want them at install time or runtime and which manifest version your extension is using.

Host permissions are specified as match patterns, and each pattern identifies a group of URLs for which the extension is requesting extra privileges. For example, a host permission could be "*://developer.mozilla.org/*".

The extra privileges include:

  • XMLHttpRequest and fetch access to those origins without cross-origin restrictions (even for requests made from content scripts)
  • the ability to read tab-specific metadata without the "tabs" permission, such as the url, title, and favIconUrl properties of tabs.Tab objects
  • the ability to inject content scripts and styles programmatically into pages served from those origins.
  • the ability to receive events from the webRequest API for these hosts
  • the ability to access cookies for that host using the cookies API, as long as the "cookies" API permission is also included.
  • bypassing tracking protection for extension pages where a host is specified as a full domain or with wildcards. Content scripts, however, can only bypass tracking protection for hosts specified with a full domain.

In Firefox, from version 56 onwards, extensions automatically get host permissions for their own origin, which is of the form:

url
moz-extension://60a20a9b-1ad4-af49-9b6c-c64c98c37920/

where 60a20a9b-1ad4-af49-9b6c-c64c98c37920 is the extension's internal ID. The extension can get this URL programmatically by calling extension.getURL():

js
browser.extension.getURL("");
// moz-extension://60a20a9b-1ad4-af49-9b6c-c64c98c37920/

API permissions

API permissions are specified as keywords, and each keyword names a WebExtension API that the extension would like to use.

These permissions are available in Manifest V2 and above unless otherwise noted:

  • activeTab
  • alarms
  • background
  • bookmarks
  • browserSettings
  • browsingData
  • captivePortal
  • clipboardRead
  • clipboardWrite
  • contentSettings
  • contextMenus
  • contextualIdentities
  • cookies
  • debugger
  • declarativeNetRequest
  • declarativeNetRequestFeedback
  • declarativeNetRequestWithHostAccess
  • devtools (This permission is granted implicitly when the devtools_page manifest key is present.)
  • dns
  • downloads
  • downloads.open
  • find
  • geolocation
  • history
  • identity
  • idle
  • management
  • menus
  • menus.overrideContext
  • nativeMessaging
  • notifications
  • pageCapture
  • pkcs11
  • privacy
  • proxy
  • scripting
  • search
  • sessions
  • storage
  • tabHide
  • tabs
  • theme
  • topSites
  • unlimitedStorage
  • webNavigation
  • webRequest
  • webRequestAuthProvider (Manifest V3 and above)
  • webRequestBlocking
  • webRequestFilterResponse
  • webRequestFilterResponse.serviceWorkerScript

In most cases the permission just grants access to the API, with the following exceptions:

activeTab permission

This permission is specified as "activeTab". If an extension has the activeTab permission, then when the user interacts with the extension, the extension is granted extra privileges for the active tab only.

"User interaction" includes:

  • the user clicks the extension's browser action or page action
  • the user selects its context menu item
  • the user activates a keyboard shortcut defined by the extension

The extra privileges are:

  • The ability to inject JavaScript or CSS into the tab programmatically (see Loading content scripts).
  • Access to the privileged parts of the tabs API for the current tab: Tab.url, Tab.title, and Tab.faviconUrl.

The intention of this permission is to enable extensions to fulfill a common use case, without having to give them very powerful permissions. Many extensions want to "do something to the current page when the user asks".

For example, consider an extension that wants to run a script in the current page when the user clicks a browser action. If the activeTab permission did not exist, the extension would need to ask for the host permission <all_urls>. But this gives the extension more power than it needs: it could now execute scripts in any tab, any time it likes, instead of just the active tab and only in response to a user action.

Note: You can only get access to the tab/data that was there, when the user interaction occurred (e.g. the click). When the active tab navigates away (e.g., due to finishing loading or some other event), the permission does not grant you access to the tab anymore.

The activeTab permission enables scripting access to the top level tab's page and same origin frames. Running scripts or modifying styles inside cross-origin frames may require additional host permissions. Of course, restrictions and limitations related to particular sites and URI schemes are applied as well.

Usually the tab that's granted activeTab is just the currently active tab, except in one case. The menus API enables an extension to create a menu item which is shown if the user context-clicks on a tab (that is, on the element in the tabstrip that enables the user to switch from one tab to another).

If the user clicks such an item, then the activeTab permission is granted for the tab the user clicked, even if it's not the currently active tab (as of Firefox 63, Firefox bug 1446956).

Clipboard access

There are two permissions which enables the extension to interact with the clipboard:

clipboardWrite

Write to the clipboard using Clipboard.write(), Clipboard.writeText(), document.execCommand("copy") or document.execCommand("cut")

clipboardRead

Read from the clipboard using Clipboard.read(), Clipboard.readText() or document.execCommand("paste")

See Interact with the clipboard for more details.

Unlimited storage

The unlimitedStorage permission:

  • Enables extensions to exceed any quota imposed by the storage.local API
  • In Firefox, enables extensions to create a "persistent" IndexedDB database without the browser prompting the user for permission at the time the database is created.

Example

json
 "permissions": ["*://developer.mozilla.org/*"]

In Manifest V2 only, request privileged access to pages under developer.mozilla.org.

json
  "permissions": ["tabs"]

Request access to the privileged pieces of the tabs API.

json
  "permissions": ["*://developer.mozilla.org/*", "tabs"]

In Manifest V2 only, request both of the above permissions.

Browser compatibility

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