The diffvap crystal dataset reports the results for high-throughput antisolvent vapor diffusion crystallization of metal halide perovskitoids. This dataset contains 918 experimental measurements previously described in Refs. Briefly, two glass vials were used for each reaction. The α vial, which contained a solution mixture of organoammonium halide salt, inorganic halide (lead iodide or bromide), solvent, and formic acid, and the β vial, which contained the volatile antisolvent (dichloromethane), were placed in a sealed chamber at an elevated temperature to allow vapor diffusion from the β vial to the α vial. The experimental setup is depicted in Fig. . The experimental outcome is a qualitative description of crystal growth. The crystal score objective has 4 options (ordered from least to most desirable): clear solution (no solid), fine powder, small crystallites, and large (> 0.1 mm) crystallites. We train an ordinal regression emulator on this dataset (see SI Sec. S.3 for further details).