tabs.sendMessage()

Sends a single message from the extension's background scripts (or other privileged scripts, such as popup scripts or options page scripts) to any content scripts or extension pages/iframes that belong to the extension and are running in the specified tab.

The message will be received in the extension context by any listeners to theruntime.onMessage event. Listeners may then optionally return something as a response back to the sender.

This is an asynchronous function that returns aPromise.

Note:You can also use aconnection-based approach to exchange messages.

Syntax

const sending = browser.tabs.sendMessage(  tabId,     // integer  message,   // any  options    // optional object)

Parameters

tabId

integer. ID of the tab whose content scripts we want to send a message to.

message

any. An object that can be serialized (seeData cloning algorithm).

optionsOptional

object.

frameIdOptional: integer. Sends the message to a specific frame identified byframeId instead of all frames in the tab. Whether the content script is executed in all frames depends on theall_frames setting in thecontent_scripts section ofmanifest.json.

Return value

APromise that will be fulfilled with the response object sent by the handler of the message in the content script, or with no arguments if the content script did not send a response.

If an error occurs while connecting to the specified tab or any other error occurs, the promise will be rejected with an error message.

If several frames respond to the message, the promise is resolved to one of answers.

Here's an example of a background script that sends a message to the content scripts running in the active tab when the user clicks the browser action. The background script also expects the content script to send a response:

// background-script.js"use strict";function onError(error) {  console.error(`Error: ${error}`);}function sendMessageToTabs(tabs) {  for (const tab of tabs) {    browser.tabs      .sendMessage(tab.id, { greeting: "Hi from background script" })      .then((response) => {        console.log("Message from the content script:");        console.log(response.response);      })      .catch(onError);  }}browser.browserAction.onClicked.addListener(() => {  browser.tabs    .query({      currentWindow: true,      active: true,    })    .then(sendMessageToTabs)    .catch(onError);});

Here's the corresponding content script:

// content-script.js"use strict";browser.runtime.onMessage.addListener((request) => {  console.log("Message from the background script:");  console.log(request.greeting);  return Promise.resolve({ response: "Hi from content script" });});