1. Mozilla
  2. Add-ons
  3. Browser extensions
  4. JavaScript APIs
  5. windows
  6. windows.onFocusChanged

windows.onFocusChanged

Fired when the currently focused window changes. Will be windows.WINDOW_ID_NONE if all browser windows have lost focus.

Note: In Windows and some Linux window managers, WINDOW_ID_NONE will always be sent immediately preceding a switch from one browser window to another.

Syntax

js
browser.windows.onFocusChanged.addListener(listener)
browser.windows.onFocusChanged.removeListener(listener)
browser.windows.onFocusChanged.hasListener(listener)

Events have three functions:

addListener(listener)

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

listener

The function called when this event occurs. The function is passed this argument:

windowId

integer. ID of the newly focused window.

Examples

Log focus changes:

js
browser.windows.onFocusChanged.addListener((windowId) => {
  console.log(`Newly focused window: ${windowId}`);
});

Example extensions

Browser compatibility

Chrome
Edge
Firefox
Opera
Safari
Firefox for Android
Safari on iOS
onFocusChanged
Chrome – Full support
Chrome 4 (Release date: 2010-01-25)
footnote Full support
Edge – Full support
Edge 14 (Release date: 2016-08-02)
footnote Full support
Firefox – Full support
Firefox 45 (Release date: 2016-03-08)
footnote Full support
Opera – Full support
Opera 15 (Release date: 2013-07-02)
footnote Full support
Safari – Full support
Safari 14 (Release date: 2020-09-16)
footnote Full support
Firefox for Android – No support
Firefox for Android
footnote No support
Safari on iOS – Full support
Safari on iOS 15 (Release date: 2021-09-20)
footnote
footnote Fires when toggling in or out of private browsing mode, leaving Safari to the home screen, and returning to Safari from the home screen.

Tip: you can click/tap on a cell for more information.

Full support
No support
See implementation notes.

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

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