The rapid expansion of the Android ecosystem is accompanied by continuing diversification of Android platforms and devices, resulting in increasing incompatibility issues. These issues not only damage user experiences and developer reputations, but also impede app development productivity and, in the longer term, the sustainability of the entire ecosystem of Android. In this paper, we conducted a large-scale, longitudinal study of compatibility issues in 62,894 benign apps developed in the past eight years, to understand the symptoms and causes of these issues. We further investigated the incompatibilities that are actually exercised at runtime through the system logs and execution traces of 15,045 apps. Our empirical findings indicate that, among others, (1) compatibility issues were prevalent and persistent at both installation and run time, with greater prevalence of run-time incompatibilities, (2) there were no certain specific Android versions that consistently saw more or less app incompatibilities than other versions, (3) installation-time incompatibilities were strongly correlated with the minSdkVersion specified in apps, while run-time incompatibilities were most significantly correlated with the underlying platform’s API level, and (4) installation-time incompatibilities were mostly due to apps’ use of architecture-incompatible native libraries, while run-time incompatibilities were mostly due to API changes during SDK evolution. We offered further insights on app incompatibilities, as well as recommendations on dealing with the issues for bother developers and end users of Android apps.