Glycosylation variants are molecular forms of a glycoprotein or other glycoconjugate that differ in their attached carbohydrate structures. A corresponding protein scaffold can carry different oligosaccharides at the same glycosylation site, producing distinct glycoforms ^[1]. Such heterogeneity arises through sequential and competing biosynthetic reactions that add, remove, or modify sugar residues ^[2]. Variation can involve sugar composition, branching, linkage, or occupancy of a glycosylation site. A preparation can therefore contain a mixture of related molecules whose carbohydrate portions have different structures ^[3]. Characterization distinguishes glycan identity and relative abundance, and can preserve information about which glycan occurs at each protein site. These structural distributions reflect the enzyme network and processing environment encountered by the molecule during synthesis and maturation ^[4].