EPP

EPP (Extensible Provisioning Protocol) is the standard XML-over-TLS protocol that domain registrars use to talk to registries. Every time a domain is registered, renewed, transferred, or has its nameservers changed, the registrar sends an EPP command (an XML document over a long-lived TLS connection) to the registry's EPP server. EPP also carries the domain status flags that surface in WHOIS, like clientTransferProhibited or pendingDelete. The user-facing surface that registrants actually touch is the per-domain auth-info code (sometimes called the auth code, EPP code, or transfer code), the password the gaining registrar needs to pull a domain over during a transfer.