Germany, Japan, and the Soviet Union used the He 100D.
Six of the prototypes were sold to the Soviet Union. All of the He 100D-0s were sold to Japan. These were to prepare Hitachi to license built the He 100s. Hitachi never built them.
Ernst Udet flew the He 100V3 to a 100 km closed circuit speed record of 394.6 mph / 635 kph in June 1938.
During 1940 the He 100D was photographed with several different unit designations to try to fool the allies into thinking there were many more He 100Ds than there really was.
The He 113s supposedly took part in providing air cover for the Scharnhorst and Gneisenau when they did their English Channel dash.
The He 100Ds were used in defense of Heinkel's factory at Rostock-Marienehe. These were flown by Heinkel's test pilots.