What are localhost and 127.0.0.1?
127.0.0.1 is a special IP address that always refers to the very computer you are using right now, and localhost is simply a name for that same address. The connection never leaves the device, so the response comes back instantly.
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Why does 127.0.0.1 always point to my own device?
The entire 127.0.0.0/8 range is reserved for loopback traffic, so a request sent to 127.0.0.1 never reaches a network card or router. It is handled directly inside the same device that sent it.
That is why 127.0.0.1 means "myself" on every computer in the world, regardless of location or provider.
Is localhost the same as 127.0.0.1?
localhost is a human-readable name that points to 127.0.0.1. Typing localhost into a browser address bar makes the computer resolve it to 127.0.0.1 automatically.
On some systems localhost resolves to the IPv6 loopback address ::1 instead, but it plays exactly the same role.
How is 127.0.0.1 different from a private IP?
A private IP, such as 192.168.0.10, can be reached by other devices on the same router, while 127.0.0.1 can only ever be reached by the device itself, never by anything else on the network.
To see how this compares with public and private addresses, read public vs private IP.
Where is 127.0.0.1 actually used?
Developers commonly use addresses like http://127.0.0.1:3000 to test a website or app locally, checking that it works before putting it on the real internet.
For your actual private and public IPs, see find your IP on Windows and find your IP on Mac.
| Item | Value | Source |
|---|---|---|
| Loopback reserved range | 127.0.0.0/8 | RFC 6890 · 2013-04 |
Frequently asked questions
Can someone use 127.0.0.1 to reach my computer remotely?
No. 127.0.0.1 always means "the device that sent this request," so if someone else connects to 127.0.0.1, they simply reach their own computer, not yours.
Are there loopback addresses other than 127.0.0.1?
The whole 127.0.0.0/8 range is reserved for loopback, so addresses like 127.0.0.2 work the same way in theory, but 127.0.0.1 is used almost everywhere by convention.
What if localhost will not load?
First confirm the service is actually running on that address, then check whether a firewall or security tool is blocking the local port, which is the usual next step.
Does a router admin page also use 127.0.0.1?
No. Router admin pages are typically reached at the router private IP, such as 192.168.0.1, which is a different address from 127.0.0.1.
Why do some apps show 127.0.0.1 with a port number, like 127.0.0.1:8080?
The number after the colon is the port, which tells the device which running program should handle the request. The same loopback address can host many different local services at once, each listening on its own port.