Note : This post is first published on Dec-2010 in my previous blog Techkindle. Moving the content here.


Firebug is an open source extension for the Mozilla Firefox Browser, which provides tools to monitor, edit, and debug any website’s CSS, HTML, DOM, and JavaScript.

It also has a JavaScript console for logging errors and watching values, as well as a “Net” feature which monitors the amount of time in milliseconds it takes to execute scripts and load images on the page.

  • CSS, HTML : In live we can edit the CSS & HTML of any web page & can view the result.
  • JavaScript : using firebug we can debug the JavaScript code by putting breakpoints & can also log the errors.
  • Network Monitor : This Feature lets you monitor how much time is spent when loading a web page. Use the Net tab to see the bar that shows when a file started and stopped loading relative to all other files. Network Monitor breaks up the traffic on a file-by-file basis so we can see how much time is spent loading image, JavaScript, HTML, and so forth.


  1. Download Firebug from
  2. Install & restart the browser.
  3. By going to any web page press f12 then you can see the window at the bottom of the page.
  • The edited HTML or CSS or JavaScript wont effect the existing code.
  • There is also a Firebug Lite version for Internet Explorer, Opera and Safari.

Happy Learning 🙂