The "Register-Registrar/Registrant" protocol is developed by Register.BG to provide access to the BG domain name registration system by the Registrars or the Registrants. For brevity the protocol will be referred to as REGRR.

Similar to the EPP protocol [RFC5730], REGRR is based on exchange of XML messages via Internet transport and permits computer to computer communication on client-server principles. The server is hosted by the Registry and the client by the Registrar or the Registrant. The REGRR protocol is designed to provide high reliability and security of the communication, by using digital signature certificates for encrypting the connection and signing the messages.

Specification of the protocol REGRR
Version	Validity date	Server	Cancellation date	Active	Download
2.0, redaction 4	12.11.2019	www.register.bg		Yes
2.0, redaction 3	03.10.2019	www.register.bg	12.11.2019	No
2.0, redaction 2	29.08.2019	www.register.bg	03.10.2019	No
2.0, redaction 1	10.04.2019	www.register.bg	29.08.2019	No
2.0	25.11.2018	www.register.bg	10.04.2019	No
2.0, preliminary	30.04.2017	bg.register.bg	25.11.2018	No
1.1, redaction 1	21.11.2012	www.register.bg	25.11.2018	No
1.1	01.03.2012	www.register.bg	21.11.2012	No
1.0	14.10.2011	www.register.bg	01.03.2012	No