The COVID-19 pandemic and the war in Ukraine emphasize the need for greater disaster resilience and preparedness. This book investigates how these apps can enhance crisis awareness and citizen involvement in disaster prevention and response. By examining user perspectives and the impact of crisis experiences, the book explores how to increase the adoption and effectiveness of warning apps. The research uses qualitative and quantitative methods, including surveys and design interventions, to reveal current usage, changes over time and desired features. It shows that while citizens find warning apps helpful, more safety-related features and two-way communication could increase their appeal. Additionally, the integration of preparedness features into these apps can increase their perceived usefulness, though challenges remain in addressing user expectations and design preferences across different crises and cultural contexts.