Usability is a quality metric that measures how easily a user interacts with an interface. It refers to the simplicity with which a product or system may be utilized to attain goals in an effective and efficient manner. The usability of digital libraries is defined by the effectiveness and efficiency of the information access system, the ease of use, the pleasantness of the user interface, user needs, usage patterns, and other aspects.

The objective of this paper is to explore the five characteristics of digital library's usability: learnability, efficiency, memorability, errors, and satisfaction. with regard to methodology, a theoretical approach was used as the research technique for this study which involves doing a review of various publications, research papers, and studies published on this topic, but it focuses more on primary sources of information. The findings of the paper demonstrates that considerable numbers of usability and evaluation studies of digital libraries have been conducted over the last two decades, using a variety of usability study tools and data collection and analysis methods. The study indicates also that research community have developed several models for the use and assessment of digital library's usability. Therefore, digital library developers should consider the five characteristics of usability while creating new digital library projects.