This paper presents a usability evaluation of a medium-fidelity prototype for a mobile platform designed to aggregate shared memories through audiovisual contributions related to cultural heritage. The platform leverages storytelling and is supported by Artificial Intelligence (AI) tools. The primary goal of this evaluation was to assess the prototype’s compliance with usability principles and heuristics, identifying and addressing potential issues with input from experts and prospective users in a controlled laboratory setting, prior to field trials at cultural events. The study was conducted in three phases. The first phase involved benchmarking prototyping and testing tools commonly used in the design and evaluation of digital products, with a focus on their features and analytical capabilities. The second phase centered on refining the medium-fidelity prototype, initially developed in Figma, to ensure alignment with Design and Usability principles. Following this, the prototype was migrated to Quant-UX, a platform offering analytical tools such as heat maps, to support the third phase of usability testing. This paper reports the outcomes of a heuristic evaluation conducted with five usability experts, alongside user testing involving twenty participants, all carried out in a laboratory environment. The experts provided technical recommendations to improve visual and textual communication, particularly concerning the platform’s structure and interactions. In parallel, user feedback offered insights into expectations and suggestions for enhancing the overall User Experience (UX). These findings are informing the iterative development of the prototype for standalone mobile use, with planned field trials during cultural events to assess the UX and performance of a high-fidelity version. Following these trials, Polariscope will be released as an open-access platform, enabling wider public engagement with and contribution to shared cultural heritage and event-based collective memories.