The study aims to measure the web impact factor of the websites of national libraries, and to indicate the extent of their electronic presence, and the extent of their impact and impact on the Internet, which amounted to 150 websites, by analyzing those websites quantitatively and qualitatively, and the study relied on the bibliometric approach using one of the methods of webometric measurements. It is the web impact factor, and the study relied on the (Google search engine) and the Way back machine. The study found that the Bahamas Library website was the largest in size and the highest online presence, while the least attended sites were the Togo and Gambia library, The Slovak Library website also scored the highest sites in terms of the overall web impact factor, and the Sweden Library website ranked first according to Web Visibility Factor. Sultan Qaboos Library ranked first for the overall web impact Factor, and the subjective web impact coefficient according to the websites of national libraries in the Arab countries. Located in the Library of Tunisia, it scored the highest rank in terms of the revised web effect coefficient, and the spider vision coefficient in the Arab countries. The study recommended the need to pay attention to webometrics, especially the web impact coefficient, and to repeat studies at varying intervals of time and compare the results.