Charity donations, as a form of resource redistribution and social investment, can explicitly or implicitly promote the achievement of multiple Sustainable Development Goals (SDGs). With advancements in technology, donation activities are no longer limited to traditional methods but can now be facilitated through digital platforms, enabling instant acts of goodwill. This study aims to explore how UI/UX prototype design influences user behavior and satisfaction, providing an alternative option for donors. The study adopts a design thinking approach, encompassing five stages: empathize, define, ideate, prototype, and test. A mixed-methods research methodology is employed, combining qualitative and quantitative techniques. The qualitative part includes two rounds of interviews. The first round aims to understand participants’ donation experiences and gather feedback on the design prototype. The testing tasks include Login, Filtering Donation Targets, Making a Donation, Activating the Automatic Donation Function, and Topping Up. The second round of interviews evaluates the improvements in user experience after modifications to the prototype, analyzed through qualitative coding. The quantitative part is based on the System Usability Scale (SUS) questionnaire to assess user satisfaction with the prototype interface. Based on participant feedback, the improved prototype introduced features such as a success pop-up and a thank-you message upon completing a donation. Notably, a donation tracking function was added, which significantly enhanced users’ trust in the application and improved the overall user experience. The results indicate positive user satisfaction with the design prototype, as evidenced by the SUS score of 66.3, corresponding to a “C” grade, an “OK” adjective rating, and a classification as “marginally acceptable,” category. The Net Promoter Score (NPS) revealed a neutral attitude from users regarding their likelihood to recommend the application. These findings provide a foundation for the further development of efficient and user-friendly digital donation applications and offer valuable insights for digital donation technologies.