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 the runtime.onMessage event. Listeners may then optionally return something as a response back to the sender.

This is an asynchronous function that returns a Promise.

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 (see Data cloning algorithm).

options Optional

object.

frameId Optional

integer. Sends the message to a specific frame identified by frameId instead of all frames in the tab. Whether the content script is executed in all frames depends on the all_frames setting in the content_scripts section of manifest.json.

Return value

A Promise 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.

Examples

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 (let 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"});
});

Example extensions

• beastify
• cookie-bg-picker
• imagify

Browser compatibility