Please note that this extension is useful for web developers only. Also available on Chrome Store Once Web Developer Sidekick installed you have to go to configuration page (about:addons) and click Options. Now you can set the addon parameters. The extension use YAML notations to read the parameters. Note: Be carefull when you add credentials for production environment since any one who has access to your browser can see those credentials. Features:

Displays website environment (screenshot 1)
Shows useful details (screenshot 2)
Extends popup byy adding new tabs (screenshots 3 & 4)
Customize addon behavior (screnshot 5)

For configuration details please check the documentation by following this link https://github.com/lahyani/web-developer-sidekick/tree/doc/doc