4-[2-(4-Chlorophenyl)hydrazinylidene]-3-methyl-1H-pyrazol-5(4H)-one

In the title compound, C10H9ClN4O, the pyrazole ring [maximum deviation = 0.014 (2) Å] forms a dihedral angle of 7.06 (14)° with the chlorobenzene ring. The molecular conformation is stabilized by an intramolecular N—H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, inversion dimers linked by pairs of C—H⋯O hydrogen bonds generate R 2 2(16) ring motifs. The dimers are further connected by N—H⋯N hydrogen bonds, thereby forming layers lying parallel to the bc plane.