index.md

---

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

---

{{AddonSidebar()}}

Warning: This is not implemented in Firefox because it has been deprecated since Chrome 33. Please use runtime.onMessage instead.

Fired when a request is sent from either an extension process or a content script.

Syntax

chrome.extension.onRequest.addListener(function(
  request,         // optional any
  sender,          // runtime.MessageSender
  () => {/* … */}  // function
) {/* … */})
chrome.extension.onRequest.removeListener(listener)
chrome.extension.onRequest.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:

    • request

      • : any. The request sent by the calling script.

    • sender

      • : {{WebExtAPIRef('runtime.MessageSender')}}.

    • sendResponse

      • : function. Function to call (at most once) when you have a response. The argument should be any JSON-ifiable object, or undefined if there is no response. If you have more than one onRequest listener in the same document, then only one may send a response.

Browser compatibility

{{Compat}}

{{WebExtExamples}}

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