This comes default with Joomla! Did you ever wonder how to remove them? Well, there are many ways to do that. I will show you the easiest one. You can do this without hacking code. I came across Joomla Plugin – Bye Bye Generator, which will do your job.
Bye Bye Generator
Very tiny plugin to do precisely – remove Meta generate. You also have the option to rename a custom generator. This is compatible with Joomla 2.5 and 3.x
Download and Install Bye Bye Generator Plugin Open the plugin from Plugin Manager Click Remove next to the generator and publish it. Refresh your Joomla website and verify with page source code
I tested and worked as expected! On a mission to secure a Joomla site? Check out security extension to protect from online vulnerabilities or consider using Cloud WAF.