The study aims to introduce the concept of Social Media Optimization)SM0), highlight the objectives and the advantages of applying it to library websites, and identify the principles of creating websites for social networks, methods and tools for their application on libraries websites. Moreover, it aims to shed light on Internet models of foreign libraries websites that have been configured for networks. The study also attempts to identify the impact of all this on increasing content participation and achieving high traffic rates for website pages and the interaction of beneficiaries with them through social networks and then explore the extent to which Smou's principles are applied to the Bibliotheca Alexandrina Internet website, and to identify the challenges facing its preparation for social media optimization.studing the Bibliotheca Alexandrina website and came up with important finding as a total of (61.17%) of the principles of creating websites for social networks on the Bibliotheca Alexandrina website was achieved. The first principle which is to prepare shareable content through social networks has been achieved by (72,73%). second principle which is facilitating content sharing has been achieved by (100%). third principle which is rewarding interaction and engagement has been achieved at a rate of (14,29%). fourth principle which is participating in the initiative with has been achieved at a percentage of (33.33). last principle which is measuring usage and encouraging Reuse has been achieved by (57.14%). The human challenges are the most important obstacles to creating website for social networks, with a percentage of (61.17%).