index.md

---

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

---

{{AddonSidebar()}}

Fired when a tab is zoomed.

Syntax

browser.tabs.onZoomChange.addListener(listener)
browser.tabs.onZoomChange.removeListener(listener)
browser.tabs.onZoomChange.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 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:

    • ZoomChangeInfo

      • : object. Information about the zoom event. See the ZoomChangeInfo section for more details.

Additional objects

ZoomChangeInfo

• tabId

  • : integer. ID of the tab that was zoomed.

• oldZoomFactor

  • : number. The previous zoom factor.

• newZoomFactor

  • : number. The new zoom factor.

• zoomSettings

  • : {{WebExtAPIRef('tabs.ZoomSettings')}}. Zoom settings for the tab.

Examples

Listen for zoom events and log the info:

function handleZoomed(zoomChangeInfo) {
  console.log(`Tab: ${zoomChangeInfo.tabId} zoomed`);
  console.log(`Old zoom: ${zoomChangeInfo.oldZoomFactor}`);
  console.log(`New zoom: ${zoomChangeInfo.newZoomFactor}`);
}

browser.tabs.onZoomChange.addListener(handleZoomed);

{{WebExtExamples}}

Browser compatibility

{{Compat}}

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