Abstract Real-time systems are notoriously hard to verify due to nondeterminism, concurrency and timing constraints. When timing constants are uncertain (in early the design phase, or due to slight variations of the timing bounds), timed model checking techniques may not be satisfactory. In contrast, parametric timed model checking synthesizes timing values ensuring correctness. takes as input an extension of parametric timed automata (PTAs), a powerful formalism to formally verify critical real-time systems. extends PTAs with multi-rate clocks, global rational-valued variables and a set of additional useful features. We describe here the new features and algorithms offered by 3, that moved along the years from a simple prototype dedicated to robustness analysis to a standalone parametric model checker for timed systems.