This paper explores the archiving of web sites of fifteen Croatian public libraries in the foreign web archive Wayback Machine and in the Croatian Web Archive. It was explored how many web sites of Croatian public libraries are archived in both archives, which are the oldest and which are the youngest web sites stored, which web sites contain the largest and which the smallest number of archived web pages, and what information about these web pages can be found when searching for them. The paper contains a review of literature and research. The review of literature part talks about archiving in general, about its beginnings and development in the world and in Croatia, as well as about web archives and their characteristics. Examples from abroad and various ways of web archiving are described. The second part of the paper is the research part: the methodology of the research, the results of the research and the discussion of the collected data are presented. Data that were collected are the date of the first and last archiving in both archives, the number of times archiving was done, the size of the archived file for the Croatian Web Archive, the existence of three levels of archiving for each web site in both archives and the appearance of archived web sites.