runtime.getBackgroundPage() - Content

Retrieves the {{DOMxRef("Window")}} object for the background page running inside the current extension. If the background page is non-persistent (an event page) and it is not running, the background page is started.

This provides a convenient way for other privileged extension scripts to get direct access to the background script's scope. This enables them to access variables or call functions defined in that scope. "Privileged script" here includes scripts running in options pages, or scripts running in browser action or page action popups, but does not include content scripts.

Note that variables that were declared using const or let do not appear in the Window object returned by this function.

Also note that this method cannot be used in a private window in Firefox—it always returns null. For more info see related bug at bugzilla.

If the background page is an event page, the system will ensure it is loaded before resolving the promise.

This is an asynchronous function that returns a {{JSxRef("Promise")}}.

[!NOTE] In Firefox, this method cannot be used in Private Browsing mode — it always returns null. For more info see Firefox bug 1329304.

In Chrome, this method is available only with persistent background pages, which are not available in Manifest V3, so consider using Manifest V2. See Migrate to a service worker for details.

Consider using {{WebExtAPIRef("runtime.sendMessage","runtime.sendMessage()")}} or {{WebExtAPIRef("runtime.connect","runtime.connect()")}}, which work correctly in both scenarios above.

Syntax

js-nolint

let gettingPage = browser.runtime.getBackgroundPage()

Parameters

None.

Return value

A {{JSxRef("Promise")}} that will be fulfilled with the {{DOMxRef("Window")}} object for the background page, if there is one. If the extension does not include a background page, the promise is rejected with an error message.

Examples

Suppose a background script defines a function foo():

// background.js

function foo() {
  console.log("I'm defined in background.js");
}

A script running in a popup can call this function directly like this:

// popup.js

function onGot(page) {
  page.foo();
}

function onError(error) {
  console.log(`Error: ${error}`);
}

let getting = browser.runtime.getBackgroundPage();
getting.then(onGot, onError);

Browser compatibility

[!NOTE] This API is based on Chromium's chrome.runtime API. This documentation is derived from runtime.json in the Chromium code.