A lot of library services are impacted by the expansion and advancement of information and communication technologies. With this modification, the traditional library services are now entirely digital. To carry out this digitalization, the Unej Digital Library (UnejDigiLib) application was created by the University of Jember's library. The purpose of developing this digital library application was to improve the effectiveness of library services, which were previously hindered by the COVID-19 epidemic. The UnejDigiLib developer has not yet evaluated the quality of its services since the application's release, therefore they are unsure of whether the current services satisfy user needs. Therefore, the goal of this study is to combine Mobile Service Quality (M-S-QUAL) and Importance Performance Analysis (IPA) in order to assess the UnejDigiLib service's quality based on user perceptions. The M-S-QUAL is used to determine service quality indicators and examine the gap between their performance and importance. After that, the service indications are mapped using the IPA based on their priority level. This study used the following six M-S-QUALl dimensions: compensation, privacy fulfillment, content, system availability, efficiency, and privacy. The findings indicate that user expectations have not been met by the UnejDigiLib service's performance. Meanwhile, the IPA analysis's findings indicate that the following indicators are found in quadrant 1: C3 (completeness of the book collection), C5 (suitability of the book collection with the curriculum lectures), C6 (updates to the book collection), and F3 (speed at which books download). This quadrant's indicators are the primary focus for improvement.