🖥️ We’ve All Used localhost But Have You Ever Wondered How It Works?

We’ve all typed localhost to test our web apps.
It’s almost like muscle memory at this point.

But only recently, I paused and thought:

“How does localhost actually work? Why does it magically know to point to my computer?”

Turns out, the answer is both simple and cool. Let's explore.

What Is localhost?

At its core, localhost is just a hostname, a label used to refer to a network device.

But unlike google.com or facebook.com, localhost always points to your own computer.

By default, it maps to:

127.0.0.1   // IPv4 loopback address
::1         // IPv6 loopback address

When your browser connects to localhost, it loops back internally to your own system, no router or internet needed.

Where Is This Mapping Stored?

That magic mapping of localhost to 127.0.0.1 happens in a simple text file called the hosts file.

On Windows:

C:\Windows\System32\drivers\etc\hosts

And inside, you’ll usually find:

127.0.0.1   localhost
::1         localhost

These lines tell your system that localhost is just another name for 127.0.0.1.

How Your OS Resolves Hostnames

Whenever you open a URL in your browser, here’s what your OS does:

1. Check the hosts file

2. If not found, ask the DNS server

3. If DNS doesn’t know, show an error

That means your system looks into the hosts file before touching the internet.

So technically, the hosts file is like a mini local DNS. You can override any domain, reroute URLs, and more.

It’s fascinating how something we use every day hides such an elegant little system under the hood.