The asymmetric unit of the title compound, C(8)H(6)N(2)O(4), contains one half-mol-ecule; a twofold rotation axis bisects the molecule. The quinoxaline ring is planar, which can be attributed to electron delocalization. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into R(2) (2)(10) motifs, leading to layers, which inter-act via phen-yl-phenyl inter-actions (C⋯C distances in the range 3.238-3.521 Å).