1. Mozilla
  2. Add-ons
  3. Browser extensions
  4. manifest.json
  5. permissions

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, each of which is a permission request.

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

    Note: For Manifest V2 extensions in Firefox only, this includes 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.
  • 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.

API permissions

You specify API permissions 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
  • tabGroups
  • tabHide
  • tabs
  • theme
  • topSites
  • unlimitedStorage
  • 'userScripts' (see userScripts permission)
  • webNavigation
  • webRequest
  • webRequestAuthProvider (Manifest V3 and above)
  • webRequestBlocking
  • webRequestFilterResponse
  • webRequestFilterResponse.serviceWorkerScript

In most cases, the permission grants access to the API only, with these exceptions:

activeTab permission

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

These interactions are known as user actions and include the user:

  • clicking the extension's toolbar button or page action.
  • selecting an extension's context menu item.
  • activating a keyboard shortcut defined by the extension (from Firefox 63).
  • clicking a button on a page bundled with the extension.
  • clicking an extension suggestion in the address bar (omnibox) (from Firefox 142).

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 intent of this permission is to enable extensions to fulfill a common use case without granting them overly 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 can 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: Your extension can only access the tab or data that existed when the user interaction occurred (e.g., a click). When the active tab navigates away (e.g., due to page load finishing or another event), the extension no longer has permission to access the tab.

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 the active tab, with one exception. An extension can create a menu item using the menus API that displays when the user context-clicks a tab. That is, a menu on an element in the tabstrip that lets the user switch between tabs. If the user clicks this menu, then the activeTab permission is granted for the tab the user clicked, even if it's not the active tab (as of Firefox 63, Firefox bug 1446956).

Clipboard access

Two permissions enable an 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.

Examples

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.

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