Make a connection between different contexts inside the add-on.

You can call this:

  • in an add-on's content scripts, to establish a connection with the add-on's background scripts (or similarly privileged scripts, like popup scripts or options page scripts).
  • in an add-on's background scripts (or similarly privileged scripts), to establish a connection with a different add-on.

Note that you can't use this function to connect an add-on to its content scripts. To do this, use tabs.connect().


var port = browser.runtime.connect(
  extensionId, // optional string
  connectInfo  // optional object


string. The ID of the add-on to connect to. The ID of the add-on to send the message to. If the target has set an ID explicitly using the applications key in manifest.json, then extensionId should have this value. Otherwise it should be have the ID that was generated for the target.
object. Details of the connection:
string. Will be passed into runtime.onConnect for processes that are listening for the connection event.
boolean. Whether the TLS channel ID will be passed into runtime.onConnectExternal for processes that are listening for the connection event.

Return value

runtime.Port. Port through which messages can be sent and received. The port's  onDisconnect event is fired if the add-on does not exist.

Browser compatibility

ChromeEdgeFirefoxFirefox for AndroidOpera
Basic support26Yes454815


This content script:

  • connects to the background script and stores the Port in a variable called myPort.
  • listens for messages on myPort and logs them.
  • sends messages to the background script, using myPort, when the user clicks the document.
// content-script.js

var myPort = browser.runtime.connect({name:"port-from-cs"});
myPort.postMessage({greeting: "hello from content script"});

myPort.onMessage.addListener(function(m) {
  console.log("In content script, received message from background script: ");

document.body.addEventListener("click", function() {
  myPort.postMessage({greeting: "they clicked the page!"});

The corresponding background script:

  • listens for connection attempts from the content script.
  • when it receives a connection attempt:
    • stores the port in a variable named portFromCS.
    • sends the content script a message using the port.
    • starts listening to messages received on the port, and logs them.
  • sends messages to the content script, using portFromCS, when the user clicks the add-on's browser action.
// background-script.js

var portFromCS;

function connected(p) {
  portFromCS = p;
  portFromCS.postMessage({greeting: "hi there content script!"});
  portFromCS.onMessage.addListener(function(m) {
    console.log("In background script, received message from content script")


browser.browserAction.onClicked.addListener(function() {
  portFromCS.postMessage({greeting: "they clicked the button!"});

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, Makyen, chrisdavidmills, TotalAMD
 Last updated by: wbamberg,