The paper deals with the emergence and development of library OPACs and includes evaluations conducted on selected OPACs of public libraries in the world and in the Republic of Croatia. The first part of the paper thus includes a review of the literature on the topic of continuous progress of library catalogs, which over time increasingly turned to the needs of users. Orientation to user needs, which over time became largely determined by the emergence of interactive interfaces on the world wide web, eventually leads to the idea of OPAC 2.0 - a variant of the library online catalog adapted to the modern user. The mentioned idea of OPAC 2.0, in addition to the envisaged advantages such as involving users in the creation of content on the interfaces of library catalogs, also encounters criticism, the review of which is presented in more detail in the paper. The evaluations conducted in this paper are focused on determining the frequency of OPAC 2.0 features in selected OPACs of five public libraries in the world and five public libraries in the Republic of Croatia. The aim was to determine which of the examined features most often and most rarely appear in the selected OPACs, to determine which OPAC 2.0 features are currently included in tested OPACs and finally to conclude the difference between world and Croatian OPACs in terms of level of development. The results of the evaluations ultimately provided a detailed view of the frequency of the examined features, which is described in more detail in the paper. Furthermore, in terms of OPAC 2.0 features, it has been shown that the World Public Libraries do include them in their OPACs, proving their positive contribution to library catalogs. In conclusion, the final comparison of the results of world and Croatian public libraries shows the advantage that world OPACs achieve, which renders them as a possible model for further progress of OPACs of public libraries in the Republic of Croatia.