Allogeneic haematopoietic stem cell transplantation is a clinical example of precision medicine, as one individual donor is selected for one individual patient based on genetic findings in the human leukocyte antigen (HLA) system. Unrelated donor search for Danish patients is based on an international collaboration between global registries hosting more than 37 million potential donors worldwide for patients in need. The implementation of next-generation sequencing technologies has been a revolution in donor registry typing due to more precise, detailed and cheaper HLA analyses, which is discussed in this review.