How To Setup Addon Domain In Namecheap And Host Multiple Websites On One Hosting 

You need to own the domain which you are adding as an addon domain. If you do not own it, you will have to purchase it

The concept is very much similar. Even if you add an addon domain to your account it will be created as a subdomain on your website. For example I created an addon domain called platformkalllada.com on Kallada Academy's hosting, it can be accessed at platformkallada.com as well as platformkallada.kalladaacademy.com

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