Guimoo: Graphical User Interface for Multi Objective Optimization Guimoo is a free software dedicated to the analysis of results in multi-objective optimization Its main features enable : The on-line visualization of approximative Pareto frontiers. Such information could be used by the expert to build more efficient metaheuristics. A Pareto frontier may be characterized by its (dis)continuity, (dis)convexity, modality, ... Some metrics for quantitative and qualitative performance evaluation (S-metric, R-metrics, contribution, entropy, generational distance, spacing, size of the dominated space, coverage of two sets and coverage difference)