Domain registrars are the companies that have been licensed by ICANN (Internet Corporation for Assigned Names and Numbers (ICANN) to register domain names and keep renewing them. You can go to tld-list.com to find the registrar who registers or renews a specific domain extension (such as .com, .xyz, .net, .org, .ai)  for registration at cheaper rates. Brandcart has partnerships with Godaddy, Porkbun, Dynadot and Netim and finds most of its sellers have an account with them.