index.md

---

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

---

{{AddonSidebar()}}

Fired when a tab is replaced with another tab due to prerendering or instant.

This event may not be relevant for or supported by browsers other than Chrome.

Syntax

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

    • addedTabId

      • : integer. ID of the replacement tab.

    • removedTabId

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

Examples

Listen for replacement events, and log the associated info:

function handleReplaced(addedTabId, removedTabId) {
  console.log(`New tab: ${addedTabId}`);
  console.log(`Old tab: ${removedTabId}`);
}

browser.tabs.onReplaced.addListener(handleReplaced);

{{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.