Why 127.0.0.1 Is Not a Public Proxy
Recognize loopback, private, and shared address ranges before trying to use an endpoint copied from a public proxy list.
If you enter 127.0.0.1 as a proxy address, your application tries to reach a service on its own machine. It does not connect back to the computer that published the address. A port such as 8080 only selects a service at that local address.
This is why a tutorial using 127.0.0.1 can work for its author and fail on your computer. The example assumes a local proxy is already running. Copying the address does not install or start that service.
Other addresses that need network context
| Range | Meaning |
|---|---|
| 127.0.0.0/8 | Loopback to the local system. |
| 10.0.0.0/8 | Private-use addresses. |
| 172.16.0.0/12 | Private-use addresses; not every address beginning with 172 is private. |
| 192.168.0.0/16 | Private-use addresses. |
| 100.64.0.0/10 | Shared address space, distinct from the private-use ranges above. |
Private addresses can identify legitimate internal proxies when you are connected to the appropriate network. They do not identify a unique public endpoint reachable from anywhere. Unrelated networks can reuse the same private range.
A syntactically valid IP is therefore not necessarily a suitable public proxy address. Public reachability is a separate question from whether the text parses as IPv4. Check the proxy protocol and expected response as well as the listening port.
What to do with a copied entry
Check whether the address is a local setup example, an internal service, or an actual public endpoint. If you intended to use a local proxy, confirm that the service is listening on the expected port. If you intended to use a public list, choose an appropriate entry from the free proxy list and its stated protocol rather than changing the port on a loopback address.