With the adoption of new technologies and the explosion of information, turned traditional library into digital one. Social Networking Sites are one of major factor of new technology which importance is growing up rapidly. Libraries are the collectors of knowledge and information and its works as a connector of information and information seeker. Social Networking sites are helping the users to access the information at least time. SNS generates an atmosphere where one can exchange their idea to others through internet. Social Networking Sites helps in becoming the world into a global village. Library activities and professionals have been upgraded due to growth of SNS. This article gives importance on various social networking sites using in the library, advantages and challenges of SNS. This article also discusses important of Social Networking sites in the library. It also includes the data collected from the user feedback of Gauhati University.