This article presents DiCo, an inventory of the changes in the nomenclature of four French dictionaries (Dictionnaire de l'Académie française, Dictionnaire Hachette, Le Petit Larousse and Le Petit Robert). For each modification recorded, DiCo provides additional information on the microstructural level, such as the linguistic labels included in the article where the change occurred. Based on a manual comparison of the successive editions of a given dictionary, DiCo can be the starting point for quantitative and qualitative metalexicographical studies. The description of the diachronic evolution of a dictionary and the comparison of different dictionaries reveal that not only does lexicographical change reflect language evolution, but that the content of a dictionary is also bound to the editorial policy of a publishing house, itself subject to change. Given the scarcity of information on this topic provided to the general public by French publishing houses, a resource facilitating metalexicographical investigations is particularly helpful. In addition to enabling a better understanding of French dictionaries, DiCo may be useful to linguists interested in lexicology and diachronic and diatopic variation. Finally, it might also prove useful for building lexicons for natural language processing.