Why is chrome.devtools.network "undefined"?

Question

I'm trying to create an extension that logs all network events. This is the code:

Manifest.json:

{
  "name": "My extension",
  "version" : "1.0",
  "background": {
    "scripts": ["background.js"],
    "persistent": true
  },
 "devtools_page": "devtools.html",
 "browser_action": {
    "default_title": "Get it",
    "default_icon" : "icon.png"
  },
  "manifest_version": 2
}

background.js:

chrome.devtools.network.onRequestFinished.addListener(function(request) {});

What's the problem? I tried a lot of things, it doesn't seem like any scripts that I link in devtools.html is getting picked up at all. No logs, no nothing. Only the background.js is doing something, and it doesn't seem to support chrome.devtools ?

Answer 1

chrome.devtools.network is only available within a devtools page. From the documentation of the devtools API (third list item):

The chrome.devtools.* API modules are available only to the pages loaded within the Developer Tools window. Content scripts and other extension pages do not have these APIs. Thus, the APIs are available only through the lifetime of the Developer Tools window.

If you need the information in the background page, have a look at this answer (full code included) for setting up a communication channel: Chrome Devpanel Extension Communicating with Background Page.