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Using Firefox' Remote Debugger from Emacs
Emacs Lisp
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I just found out that a similar project which also includes Chrome support exists:


Since version 15 Mozilla Firefox comes with a remote debugging protocol. This was introduced to support debugging for Firefox on Android and FirefoxOS. But it can also be activated for regular Firefox although it requires a bit of extra work at the moment (Firefox 19).

This Emacs package provides a basic implementation of the protocol for Emacs. So far only the lowlevel communication structure is done.

Configuring Firefox

Go to about:config and set the following paramters: devtools.debugger.remote-enabled to true and devtools.debugger.force-local to false and to true and restarted firefox.

Open a Scratchpad (Shift+F4 or WebDeveloper menu entry) and select in the Environment menu the “Browser” option. Copy and paste the following script and eval it with C-r.

const Cu = Components.utils;


function startDebuggerServer()
  // Start the server.
  if (!DebuggerServer.initialized) {
  // For an nsIServerSocket we do this:
  DebuggerServer.openListener(6000); // A connection on port 6000.


Basic Usage

(let ((con (firefox-remote-connect "localhost" 6000)))
  (firefox-remote-send con '((to . root) (type . listTabs))
                       (lambda (data)
                         (let* ((selected (cdr (assq 'selected data)))
                                (tabs (cdr (assq 'tabs data)))
                                (current-tab (aref tabs selected))
                                (url (cdr (assq 'url current-tab)))
                                (title (cdr (assq 'title current-tab))))
                           (message "Current Tab \"%s\": \"%s\"" title url))))
  (sleep-for 10)
  (firefox-remote-disconnect con))

This should print the title and url of the currently selected tab to the *Messages* buffer.

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