Loopback address
::1
::1 is IPv6's loopback address (RFC 4291). It isn't routed on the public internet, so there's nothing public to look up. IPv6's localhost. Software listening on ::1 can only be reached from the same computer.
At a glance
- Block
- ::1/128
- Defined in
- RFC 4291
- On the public internet
- No
About this block
Traffic to a loopback address never leaves the device: the operating system hands it straight back. 127.0.0.1 is what the name localhost points to, and the whole 127.0.0.0/8 block works the same way. In IPv6 there's just one, ::1.
Every computer has its own, so a loopback address always means “this machine”.
Where you'll see it
- Development servers listening at 127.0.0.1 or localhost, which only that computer can reach.
- Hosts files and ad blockers that point names at 127.0.0.1 so they go nowhere.