qpOASES is an open-source C++ implementation of the recently proposed online active set strategy for solving quadratic programming (QP) problems. It has several theoretical features that make it particularly suited for model predictive control (MPC) applications. Further numerical modifications have made qpOASES a reliable QP solver, even when tackling semi-definite, ill-posed or degenerated QP problems. Moreover, several interfaces to third-party software make the code easy-to-use. qpOASES has been under development since 2007 and has proven useful in numerous real-world applications and industrial projects.