The title compound, C6H6N4S, crystallizes with two independent molecules, A and B, in the asymmetric unit. Both independent molecules are almost planar [maximum deviations of 0.068 (6) A ° in molecule A and 0.079 (6) A ° in molecule B]. In the crystal, molecules A and B are linked by N—H  S, N—H  N and C—H  S hydrogen bonds, forming a threedimensional network.