It can be made by reacting anhydrous (without any water molecules attached) cobalt(II) oxide or cobalt(II) chloride with a stream of hydrogen fluoride. This reaction makes the anhydrous form. The hydrated (with water molecules attached) form is made by reacting any cobalt(II) compound with hydrofluoric acid. When fluorine is reacted with cobalt at a high temperature, it makes both cobalt(II) fluoride and cobalt(III) fluoride.