Purpose. Nowadays, it is difficult to imagine a person who would not use a smartphone. The main direction in creating many applications are such operating systems as iOS and Android. One of the essential stages of the life cycle of cross-platform applications for iOS and Android is building architecture. It is important not only to be able to build an architecture using well-known «tools», but also to understand to which extent this should be implemented and what impact it will have on the software product in the future. The aim of the work is to analyze approaches to development with excessive or insufficient use of design principles and templates, as well as analysis of the results of the final product, cross-platform software for iOS and Android operating systems. Methodology. To improve the existing software, a static analyzer has been designed and implemented, which is focused on the development of architecture in software of different sizes and types. Only the necessary templates and design approaches which allowed implementing the necessary functionality without complicating the system and guarantee easy support, testing and extension of functionality if it is needed, were used to create the software product. Findings. During the experiments, it was found that when designing cross-platform software for iOS and Android operating systems, not only neglect of patterns and common design approaches, but also their excessive use complicates the development, expansion, maintenance and testing of software. Originality. The extent and consequences of using the design templates, the benefits and examples of using the patterns and approaches in the design of cross-platform applications were determined. For the first time, the necessary degree of use of design templates for mobile applications of different sizes and purposes was analyzed. Practical value. The results of the work will allow the programmer to better understand the principles of designing the applications for iOS and Android operating systems, as well as the conditions of use of the known design templates. The information obtained can be used by teachers of higher education institutions as a means of providing practical examples and demonstrations for higher education students in performing practical work and programmers on real commercial projects.