A fail-secure lock stays locked when power fails, so the secured side remains secured during an outage. It is used on doors where asset protection matters more than automatic release, and it requires a key or an exit device to leave. The choice between fail-safe and fail-secure is a life safety decision.
Fail-secure is the opposite of fail-safe, and the two names are easy to confuse under pressure. The behavior on power loss is the whole difference.
Security during an outage
An electric strike can be configured to stay latched without power, and a powered deadbolt behaves the same way. The door remains locked through a power cut or a controller failure, which protects a server room, a pharmacy or a records store. Staff still need a mechanical way out.
Pairing it with free egress
A fail-secure door must still allow exit, usually through a lever, a thumbturn or an exit device that works without power. Confirm the arrangement with the code official, because the lock can be secure on one side and open on the other. Test it with the power off, not just with a credential.