The Global Disaster Alert and Coordination System (GDACS) is a web-based platform that in case of natural disasters, such as earthquakes, tsunamis, floods and cyclones, sends automatic alerts via e-mail, fax or SMS to the international first responders community. GDACS combines information on the event, the population in the affected area and the vulnerability of that population to derive an alert level that indicates the probability for a catastrophic situation with needs for international humanitarian intervention. GDACS also offers a platform for structured information exchange between responders and coordinators, thus facilitating decision-making. GDACS has now 18,000 users worldwide.