index.md

---

title: windows.onCreated
slug: Mozilla/Add-ons/WebExtensions/API/windows/onCreated
page-type: webextension-api-event
tags:
  - API
  - Add-ons
  - Event
  - Extensions
  - Non-standard
  - Reference
  - WebExtensions
  - Windows
  - onCreated
browser-compat: webextensions.api.windows.onCreated

---

{{AddonSidebar()}}

Fired when a window is created.

Syntax

browser.windows.onCreated.addListener(listener)
browser.windows.onCreated.removeListener(listener)
browser.windows.onCreated.hasListener(listener)

Events have three functions:

• addListener(callback)

  • : Adds a listener to this event.

• removeListener(listener)

  • : Stop listening to this event. The listener argument is the listener to remove.

• hasListener(listener)

  • : Check whether a listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

• callback

  • : Function that will be called when this event occurs. The function will be passed the following arguments:

    • window

      • : A {{WebExtAPIRef('windows.Window')}} object containing details of the window that was created.

Browser compatibility

{{Compat}}

Examples

Log the IDs of new windows as they are created:

browser.windows.onCreated.addListener((window) => {
  console.log(`New window: ${window.id}`);
});

{{WebExtExamples}}

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