We describe the Library of Experimental Phase Relations (LEPR), which is a new Web‐based database of experiments pertaining to magmatic phase equilibria. The database includes information from experiments related to natural or near‐natural magmatic silicate phase equilibria. At present, the database includes more than 6,600 experiments with liquids ranging in composition from komatiite to rhyolite performed at temperatures between 500 and 2500°C and at pressures up to 27.5 GPa. Here we describe the organization of data and metadata that are included in the database as well as the database structure and the implementation of its Web interface. We discuss a number of challenges and considerations related to construction of a database of experimental data that influence both the selection and presentation of the information incorporated in LEPR. Finally, we survey durations of experiments in LEPR and discuss the relationship between duration and the probability of crystal‐liquid equilibrium in petrologic experiments.