A registrar-side setting that prevents unauthorized domain transfers out of your current registrar by blocking EPP authcode issuance and transfer requests. It's a basic anti-hijack mechanism.
When enabled, you cannot transfer your domain to another registrar without first disabling the lock—usually via your registrar's control panel or support ticket. The lock does not protect against compromised registrar accounts, DNS hijacking, or registry-level takeover. Some registrars enable it by default; others require you to turn it on.
Registrar lock is weaker than registry lock, which sits at the authoritative registry level and is harder to circumvent. A paranoid operator uses both. Bunkerdomains keeps registrar lock disabled by default because we assume you know your own security posture; you can enable it in your account if you want the extra friction. If you forget to disable it before a legitimate transfer, you'll hit a support queue—plan accordingly.