Electronic health records (EHR) have become a central feature of care delivery in the United States over the past decade. While the value of clinical data stored within EHRs has long been recognized as transformational for research and operational quality improvement, less well known is the metadata regarding EHR use itself, often referred to as audit logs, event logs, or EHR use metadata. EHR audit log metadata, required for security purposes, has increasingly been repurposed to understand how clinicians and patients work, interact with technology, and communicate with each other. This chapter describes what EHR audit log data are how researchers have used the “digital trails” left by normal EHR use to generate new insights across multiple domains, ranging from quantifying the time clinicians spend in the EHR to defining how teams are structured and understanding the impact of policy and reimbursement on clinician work. We then highlight important considerations for those interested in using audit logs in their own work. Finally, we propose new directions for audit log research to ensure it is robust, actionable, and relevant to the concerns of policymakers, health system leaders, and practicing clinicians.