A 2-azido analog of D-galactose in which the C2 amine (in GalN/GlcN/ManN) or hydroxyl is replaced by an azide. Used in metabolic glycoengineering and chemical reporter strategies: when supplied to cells, the analog is processed by the salvage pathway and incorporated into cell-surface glycans, where the azide handle can be detected or tagged via bioorthogonal click chemistry — copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkynes or copper-free strain-promoted cycloaddition (SPAAC) with DBCO and related strained alkynes — enabling glycan imaging, enrichment, and glycoproteomic analysis.