This thesis deals with the usability of selected TLS libraries, their documentation, code samples and related resources. We describe the design and results of our initial exploratory study and a follow-up study, both performed with students of the Faculty of Informatics. The results show that the selected libraries’ documentation suffers from many usability problems. Although these issues are not specific to TLS libraries, their consequences might be more serious. Quantitative rating of the severity of selected problems suggests that the libraries are comparable.