The properties of the human Y chromosome - namely, male specificity, haploidy and escape from crossing over - make it an unusual component of the genome, and have led to its genetic variation becoming a key part of studies of human evolution, population history, genealogy, forensics and male medical genetics. Next-generation sequencing (NGS) technologies have driven recent progress in these areas. In particular, NGS has yielded direct estimates of mutation rates, and an unbiased and calibrated molecular phylogeny that has unprecedented detail. Moreover, the availability of direct-to-consumer NGS services is fuelling a rise of 'citizen scientists', whose interest in resequencing their own Y chromosomes is generating a wealth of new data.