This paper illustrates the heuristic evaluation of a web-based tool for usability testing for Public Administrations called eGLU-box. eGLU-box is an online platform aiming at supporting practitioners in the process of designing usability tests, analyzing data, and helping step-by-step participants to complete assessment tasks. Web users of Public Administrations can report their perceived quality of experience by completing a library of questionnaires shown to them by eGLU-box at the end of the test. This work is part of a multi-step user experience (UX) evaluation methodology to assess the platform. The UX evaluation methodology of eGLU-box uses standard and bio-behavioural evaluation methods. This work shows the results of the heuristic evaluation of eGLU-box involving five human factors experts and 20 practitioners working in Italian Public Administrations. Findings show that most of the problems are rated as minor problems and related to Nielsen’s heuristic, “visibility of the system.” Only 9% of problems are rated as major problems. These major problems are related to the “problematic match between system and the real world” heuristic. Evaluators provided indications for improvements that will be applied for the next version of the platform.