Loopback address
127.0.0.1
127.0.0.1 is in 127.0.0.0/8, the loopback block (RFC 1122). It isn't routed on the public internet, so there's nothing public to look up. The address localhost points to. Software listening on 127.0.0.1 can only be reached from the same computer.
At a glance
- Block
- 127.0.0.0/8
- Defined in
- RFC 1122
- 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.