Glossary / Networking & connectivity

localhost (127.0.0.1)

localhost is the address a machine uses to talk to itself — reserved IP 127.0.0.1 — where developers run applications during development, reachable from that machine only. It's the sandbox where changes are exercised before any server sees them. When you hear "it works on localhost", the unfinished half of the sentence is "…and now we find out about the real environment."