Constraint optimization, or constraint programming, is the name given to identifying feasible solutions out of a very large set of candidates, where the problem can be modeled in terms of arbitrary constraints. 'MiniZinc' is a free and open-source constraint modeling language. Constraint satisfaction and discrete optimization problems can be formulated in a high-level modeling language. Models are compiled into an intermediate representation that is understood by a wide range of solvers. 'MiniZinc' itself provides several solvers, for instance 'GeCode'. R users can use the package to solve constraint programming problems without using 'MiniZinc' directly, modify existing 'MiniZinc' models and also create their own models.