The Power of Words: A Comprehensive Analysis of Rationales and Their Effects on Users' Permission Decisions

—Rationales offer a method for app developers to convey their permission needs to users. While guidelines and recommendations exist on how to request permissions, developers have the creative freedom to design and phrase these rationales. In this work, we explore the characteristics of real-world rationales and how their building blocks affect users’ permission decisions and their evaluation of those decisions. Through an analysis of 720 sentences and 428 screenshots of rationales from the top apps of Google Play, we identify the various phrasing and design elements of rationales. Subsequently, in a user study involving 960 participants, we explore how different combinations of phrasings impact users’ permission decision-making process. By aligning our insights with established recommendations, we offer actionable guidelines for developers, aiming to make rationales a usable security instrument for users.