Firebug is a basic add-on that available in Mozilla Firefox, it is used to query web elements and to gain their unique identifiers.
How to install?
The installation process is really simple, nothing that should challenge you, just follow this basic steps.
Step 1: open the Mozilla Firefox browser.
Step 2: Navigate to the Mozilla Firefox Add-ons center, this link will do the work:
Step 3: Under the “Firebug” Grid, Select the “+ ADD to Firefox”
Step 4: in the security “pop-up”, select “Allow”
Step 5: Firefox starts the download process, after download completed, you will see the “Software Installation” window, Select “install”
Step 6: Once the installation process is finished, you will see a notification indicates that the installation process is finished and that the “Firebug” add-on is now available and ready for use.