Personas, initially originated in user experience research, are short and simplified representations of particular user groups, and this methodological approach has recently gained ground in educational research. This study aims to explore aspects of personas that may be beneficial for prospective mathematics teachers when they develop digital learning resources. To explore such aspects, we employed qualitative interviews, thinking-out-loud techniques, and jointly developed learning resources with prospective mathematics teachers, and analysed this diverse data with a combination of case study and grounded theory approaches. Consequently, we were able to identify the following essential aspects of using personas in our study: (A) personas as representatives of real people, (B) personas as planning & feedback tools for material development, (C) professionalisation of prospective mathematics teachers (by using personas), (D) differentiation/individualisation for personas through digital learning resources, and (E) motivational elements of digital mathematics learning resources. Based on our results, we concluded that using personas could broaden prospective mathematics teachers' views on student characteristics and demands that may enable teachers to facilitate the development of differentiated and individualised digital mathematics learning resources.