COSYS is an open computational platform designed for the Systems Biology community. Designed to help life scientists to easily access basilar systems biology tools, it can be also used with effectiveness by skilled systems biologists. Cooperation-driven and user-friendly, COSYS is a unified tool for biological modeling (mechanistic and constraint-based), simulation and analysis, providing users with the cutting edge of GPU-powered computation. COSYS is free of charge, and can be used by everyone.