I am not going to target Firefox in this page but I am sure that by this time there is a plugin also for other browsers.
As i use Chrome i had to install the plugin available from this page.
Once installed open it and configure it so that it is enabled for your domain
- Open the Chrome settings page for extensions configuration as shown in this image
- Click on options and the Xdebug configuration page will open
- Add your localhost domain or any other local domain you are using to the list of allowed domains on this page. For instance, in my settings above the plugin is enabled only for localhost and for wallet.dev