This chapter discusses the reliability of a mobile application as one of the main quality attributes. This chapter considers the stability of a mobile application in terms of providing a mobile application without errors in the script or unhandled exceptions, or any other types of crashes. The focus is on the ability of a mobile application to discover, adapt, prevent, and recover from any mobile operational issues. This chapter emphasizes the possibility of the mobile operation to recover after any fatal mistake and continue to use the same mobile application even after a serious problem. Besides, it focuses on data integrity and discusses different behavioral issues of the application, such as predictability, consistency, and trustworthiness.