Utilities related to your add-on. Get URLs to resources packages with your add-on, get the Window object for your add-on's pages, get the values for various settings. Note that the messaging APIs in this module are deprecated in favor of the equivalent APIs in the runtime module.


The type of extension view.


Set for the lifetime of a callback if an ansychronous extension api has resulted in an error. If no error has occured lastError will be undefined.
True for content scripts running inside incognito tabs, and for extension pages running inside an incognito process. The latter only applies to extensions with 'split' incognito_behavior.


Converts a relative path within an extension install directory to a fully-qualified URL.
Returns an array of the Window objects for each of the pages running inside the current extension.
Returns the Window object for the background page running inside the current extension. Returns null if the extension has no background page.
Retrieves the state of the extension's access to Incognito-mode (as determined by the user-controlled 'Allowed in Incognito' checkbox).
Retrieves the state of the extension's access to the 'file://' scheme (as determined by the user-controlled 'Allow access to File URLs' checkbox).
Sets the value of the ap CGI parameter used in the extension's update URL. This value is ignored for extensions that are hosted in the browser vendor's store.


Fired when a request is sent from either an extension process or a content script.
Fired when a request is sent from another extension.

Browser compatibility

Chrome Edge Firefox Firefox for Android Opera
ViewType Yes No 45.0 48.0 33
getBackgroundPage Yes Yes 45.0 48.0 33
getExtensionTabs Yes No No No No
getURL Yes Yes 45.0 48.0 33
getViews Yes No 45.0 48.0 33
inIncognitoContext Yes No 45.0 48.0 33
isAllowedFileSchemeAccess Yes No 48.0 48.0 33
isAllowedIncognitoAccess Yes No 48.0 48.0 33
lastError Yes No 47.0 48.0 33
onRequest Yes No No No 33
onRequestExternal Yes No No No 33
sendRequest Yes No No No No
setUpdateUrlData Yes No No No 33

Chrome incompatibilities

  • Firefox does not support:
    • setUpdateUrlData()
  • Additionally, the following deprecated properties will not be supported:
    • onRequest
    • onRequestExternal
    • getExtensionTabs()
    • sendRequest()

Example add-ons


This API is based on Chromium's chrome.extension API. This documentation is derived from extension.json in the Chromium code.

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

 Contributors to this page: wbamberg, bsilverberg
 Last updated by: wbamberg,