windows.onFocusChanged

Fired when the currently focused window changes. Will bewindows.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

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. Thelistener argument is the listener to remove.
hasListener(listener): Check whether alistener is registered for this event. Returnstrue 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:

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

Example extensions

bookmark-it

Browser compatibility

Note:This API is based on Chromium'schrome.windows API. This documentation is derived fromwindows.json in the Chromium code.

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This page was last modified on⁨Jul 17, 2025⁩ byMDN contributors.

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