What is .localhost?
The .localhost domain is typically configured to point to your device, i.e. to IP address 127.0.0.1 (IPv4) or ::1 (IPv6). This is known as a loopback, and it is widely used in software development and testing when an application needs to connect to another service running on the same device.
For further information, see Special-Use Domain Names (RFC 6761) and Reserved Top Level DNS Names (RFC 2606).
You can't register a name under .localhost at any registrar, and it's not meant to resolve on the public internet. That's exactly why it's useful: software and people can rely on it never colliding with a real website.
.localhost FAQ
Can I buy a .localhost domain?
No. .localhost is reserved by IANA for a special purpose and is not open for registration.
What is .localhost used for?
Refers to the same device.
Sources
Data from IANA root zone version 2026102000. Spotted something wrong? Tell us.