Through these developments, in-depth qualitative and quantitative characterization of all glycoproteoforms of proteins has come within reach, including for very complex viral glycoproteins. In parallel, recent advances in mass spectrometry have advanced the field of glycoproteomics, especially through new selective enrichment techniques, glycopeptide fragmentation techniques, and dedicated database search algorithms. Advances in cryo electron microscopy have made these heavily glycosylated viral proteins more feasible targets for structural studies, however, and the presence of these glycans has certainly also become more visible and is making its way to the forefront of the structural analyses. A major analytical challenge to characterize the glycans on these viral proteins is that they are notoriously heterogeneous and dynamic, making it hard to either crystallize or assign densities in the reconstructed three-dimensional maps. The field of structural virology has generated beautiful high-resolution structures of viral glycoproteins through crystallography and electron microscopy, especially of the polypeptide chain, whereas the attached glycans have remained largely elusive or rather even ignored. Third, we will review recent advances in mass spectrometry to discover how viral proteins, especially those in the viral envelope, are extensively decorated by protein glycosylation and how this influences the interactions with the host. Especially hydrogen–deuterium exchange mass spectrometry is sensitive to monitor such conformational changes and dynamics and we will describe here how this technique has advanced over the last years to tackle larger macromolecular machineries including viruses, and how that has expanded our knowledge about virus assembly, stability and conformational dynamics. Also, self-assembly and disassembly of the capsid proteins is a major quaternary structural rearrangement, often guided by conformational changes in the assembling building block. (3,4) These “breathing” motions and the capsid maturation process happen through cooperative structural and conformational changes in the proteins of the capsid, matrix, and envelope. (2) For enveloped viruses, the structural dynamics of the surface glycoproteins play a crucial role in membrane fusion and cell entry, and conformational changes of receptor binding domains play an important part in balancing immune evasion with host interactions. For instance, some capsid shells can expand their diameters by as much as 25%, (1) or dynamically flip internal capsid components to the outside to bind receptors or help lyse the host membrane to enter the cell. It is well-known that structural dynamics are essential for viral infection and replication. The study of dynamic structural behavior in proteins is particularly challenging for most analytical techniques, whereby especially crystallography and cryo-EM are biased to well-ordered structural components and generally rely on interpolation of rigid structural snapshots to infer dynamics. Second, we will review how mass spectrometry can be used to study conformational dynamics of viruses and viral proteins.