A synthetic disaccharide with the GlcNAcβ1-4GlcNAc sequence (N,N′-diacetylchitobiose), the conserved core disaccharide of all N-linked glycans and the repeat unit of chitin. Used as a probe and reference standard for N-glycan biosynthesis research, as a substrate for chitinases and endo-β-N-acetylglucosaminidases (e.g., Endo H, Endo F), and as a probe for chitin- and chitobiose-recognizing lectins.