Many a Little Makes a Mickle: A Code-Centric Empirical Study of Data Minimization Principle in Android App Development

Modern mobile applications consume large amounts of data to function, raising significant privacy concerns and regulatory challenges. While prior work has primarily focused on detecting compliance gaps through policy analysis, there remains a lack of actionable guidance for developers to implement privacy principles at the code level. In this paper, we focus on data minimization as a developer-operationalizable principle and investigate its realization in Android applications. We conduct a formative study on 1,114 open-source Android apps to identify ten recurring data minimization scenarios across five data-handling stages. Building on this, we perform a large-scale analysis of 9,875 real-world APKs and distill 31 actionable coding guidelines to support privacy-compliant development. We further examine LLM-based code generation in Android development and find that state-of-the-art models consistently reproduce data minimization-risky practices, indicating that they inherit and amplify patterns from real-world code. Encouragingly, incorporating our guidelines eliminates these issues across all evaluated models. Our work advocates a shift toward responding to privacy regulatory requirements at their code-level root causes, enabling better compliance in both human and AI-assisted programming.