DescriptionModern day smartphones have access to unprecedented levels of user privacy data. Naturally, privacy concerns and protection from security breaches, create consider- able challenges to designers as well as increase the responsibility of end-users. To address these challenges, this work focuses on 1) how to effectively supply feedback to users about their private data access on their phones and 2) how to help users make informative decisions based on this feedback. Supplying effective run-time dis- closures can help users effectively be aware of their personal data’s usage by apps on their phones without distracting them from their main task. By extracting the most useful information pertaining to data exposure would save users time and allow them to make informative decisions about their own apps’ data access. First, we explored the run-time disclosures of location access on Android phones and carried out a four-week field study. The study suggested that our run-time dis- closures were effective in informing users of their apps’ location access and had helped users to take actions to control their apps’ location access on their phones. Second, we conducted an online survey to investigate Android users’ understandings and privacy expectations of the location permissions on Android phones. The survey showed that users had a varied understanding of the approximate location permissions and their attitudes toward the privacy protection of the approximate location depended on their understanding of location accuracy. Third, we carried out a two-week field study to investigate the effectiveness of run-time disclosures with control options of apps’ permissions request on Android phones. The permission field study showed that almost all of the participants would like to receive run-time disclosures about their apps’ permission request. The participants liked the instant control options; however, too many and too frequent run-time disclosures were considered interruptive and decreased participants’ willingness to read the disclosure contents and take effective action.