Canonicalization is the process to choose url from several choices which refers to home page. For example, consider following urls 1) http://www.example.com 2) example.com/ 3) http://www.example.com/index.html 4) example.com/home.asp. These All are the same urls but crawler consider this differently. the “canonical tag ” is used to tell crawler that specific url is original copy of website. Add given markup to the original url. <link rel=”canonical” href=”original url”>. Also you can add above markup to the duplicate urls.