A drop registrar is a domain name registrar

Domain name registrar

A domain name registrar is an organization or commercial entity, accredited by both ICANN and generic top-level domain registry to sell gTLDs and/or by a country code top-level domain registry to sell ccTLDs; to manage the reservation of Internet domain names in accordance with the guidelines of...

 who registers expiring Internet domain names immediately after they expire and are deleted by the domain name registry

Domain name registry

A domain name registry is a database of all domain names registered in a top-level domain. A registry operator, also called a network information center , is the part of the Domain Name System of the Internet that keeps the database of domain names, and generates the zone files which convert...

. A drop registrar will typically use automated software to send up to 250 simultaneous domain name registration requests in an attempt to register the domain name first. In recognition of the potential abuse of such a "domain land rush", ICANN

ICANN

The Internet Corporation for Assigned Names and Numbers is a non-profit corporation headquartered in Marina del Rey, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly...

 and VeriSign

VeriSign

Verisign, Inc. is an American company based in Dulles, Virginia that operates a diverse array of network infrastructure, including two of the Internet's thirteen root nameservers, the authoritative registry for the .com, .net, and .name generic top-level domains and the .cc and .tv country-code...

 limited the number of simultaneous requests to 250 since July 17, 2001.

Drop registrars usually work for a domain back-order service, and receive a percentage of the final auction price.