Background and goals This study empirically summarizes the extent of the similarities and concentrations in the mix of winegrape cultivars across countries. It also seeks to determine by how much these mixes are becoming more or less similar, and more or less concentrated, in terms of growing area by winegrape cultivar. Methods and key findings Using a database of growing area by cultivar that accounts for 99% of the world’s winegrape growing area, we analyze similarities and concentrations in the mixes of winegrape cultivars using two indices (including a new cultivar concentration index) in innovative ways. The results show a great diversity across countries in terms of both similarities and concentrations, while providing robust evidence that the mixes of winegrape cultivars are becoming more similar across countries, and between countries and the world as a whole, and that these mixes are also becoming more concentrated within countries and globally. Conclusions and significance The results point to the increasing scope for grapegrowers to diversify and differentiate their product by choosing less-frequently planted cultivars, but they also suggest most grapegrowers have found it more profitable to move toward mainstream cultivars.