sendMessage from extension background or popup to content script doesn't work

Question

I know that question has been repeatedly asked in different ways, but I tried to go through all the answers (hopefully I didn\'t miss anyone) and none of them worked for me.

Answer 1

@apsillers is correct. Also don't forget to return true in your content-script listener or it might close too early.

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
    console.log(message)
    return true
});

Answer 2

My use-case required sending a message to the background script from a webpage. I used chrome.runtime.onMessageExternal to catch this message.

Inside of this listener I was basically forwarding the message over to my content script so it could do its thing, but I could not figure out why my content script onMessage listener wouldn't catch the message.

Turns out by waiting for 1 second before sending the message from the webpage (I was basically doing it on load) I was able to see the message hitting my content script.

Answer 3

Here's an example of a background script that sends a message to the content-script file.

background.js

chrome.tabs.sendMessage(tabs[0].id,"your message"); 

content-script/content.js

chrome.runtime.onMessage.addListener(function (response, sendResponse) {
          console.log(response);
});

Answer 4

In your background page you should call

chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
    chrome.tabs.sendMessage(tabs[0].id, {action: "open_dialog_box"}, function(response) {});  
});

instead of using chrome.extension.sendMessage as you currently do.

The chrome.tabs variant sends messages to content scripts, whereas the chrome.extension function sends messages to all other extension components.