In the title compound, C(6)H(9)N(3)O(3), the 3-diazo-2-oxopropan-amide section of the mol-ecule is nearly planar, with a maximum deviation of 0.025 (1) Å from the mean plane of its constituent atoms. The diazo C=N=N angle is 178.0 (3)°. In the crystal, pairs of inter-molecular O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into infinite double chains along the [100] direction. The double ch...