Sends a single message to event listeners within your extension or a different extension.

It works just like runtime.connect, but only sends a single message, with an optional response.

If sending to your extension, the runtime.onMessage event will be fired in each page. If sending to a different extension,  runtime.onMessageExternal will be fired.

This is an asynchronous function that returns a Promise.

Note: Extensions cannot send messages to content scripts using this method. To send messages to content scripts, use tabs.sendMessage.


var sending = browser.runtime.sendMessage(
  extensionId,             // optional string
  message,                 // any
  options                  // optional object


string. The ID of the extension to send the message to. If omitted, the message will be sent to your own extension.
any. An object that can be serialized to JSON.
boolean. Whether the TLS channel ID will be passed into runtime.onMessageExternal for processes that are listening for the connection event.

Return value

A Promise. If the sender sent a response, this will be fulfilled with the response as a JSON object. Otherwise it will be fulfilled with no arguments. If an error occurs while connecting to the extension, the promise will be rejected with an error message.

Browser compatibility

Chrome Edge Firefox Firefox for Android Opera
Basic support Yes Yes 45.0 48.0 33

Compatibility notes


  • The 'options' parameter is not supported.


Here's a content script that sends a message to the background script when the user clicks the content window. The message payload is {greeting: "Greeting from the content script"}, and the sender also expects to get a response, which is handled in the handleResponse function:

// content-script.js

function handleResponse(message) {
  console.log(`Message from the background script:  ${message.response}`);

function handleError(error) {
  console.log(`Error: ${error}`);

function notifyBackgroundPage(e) {
  var sending = browser.runtime.sendMessage({
    greeting: "Greeting from the content script"
  sending.then(handleResponse, handleError);  

window.addEventListener("click", notifyBackgroundPage);

The corresponding background script looks like this:

// background-script.js

function handleMessage(request, sender, sendResponse) {
  console.log("Message from the content script: " +
  sendResponse({response: "Response from background script"});


Example add-ons


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

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

 Contributors to this page: wbamberg, jsnjack, Makyen, chrisdavidmills
 Last updated by: wbamberg,