Mobile messaging apps are the fastest-growing digital communications phenomenon ever. Today, more than 2.5 billion people around the world use messaging apps, a figure that is expected to rise to 3.6 billion by 2018 – that’s almost half of the world’s population. Messaging apps have great potential to make a positive impact in situations of crisis. They can also introduce risks relating to security, data protection and privacy. Humanitarian organizations need to better understand the opportunities and risks in order to develop responsible, effective and safe ways to use messaging apps to meet the needs of people affected by armed conflicts, internally displaced people, refugees or migrants. The ICRC, together with The Engine Room and Block Party, has produced this report on the current and potential uses of messaging apps such as Facebook Messenger, WhatsApp and Snapchat in humanitarian situations.