Abstract—Performance of rapidly evolving mobile apps is one of the top concerns for users and developers nowadays. Despite the efforts of researchers and mobile API designers to provide developers with guidelines and best practices for improving the performance of mobile apps, performance bottlenecks are still a significant and frequent complaint that impacts the ratings and apps ’ chances for success. However, little research has been done into understanding actual developers ’ practices for detecting and fixing performance bottlenecks in mobile apps. In this paper, we present the results of an empirical study aimed at studying and understanding these practices by surveying 485 open source Android app and library developers, and manually analyzing performance bugs and fixes in their app repositories hosted on GitHub. The paper categorizes actual practices and tools used by real developers while dealing with performance issues. In general, our findings indicate that developers heavily rely on user reviews and manual execution of the apps for detecting performance bugs. While developers also use available tools to detect performance bottlenecks, these tools are mostly for profiling and do not help in detecting and fixing performance issues automatically. Index Terms—Performance, Bottlenecks, Developers, Android I.