Getting Started with cURL – A Beginner’s Guide to Talking to Servers

What is a Server?

A server is just a computer that:

• Stays online always

• Waits for requests

• Sends responses back

That’s it.

Your device sends a request → a server processes it → the server sends a response.

Examples:

• A browser asks for a webpage → server returns HTML

• Your frontend asks your backend → backend returns data

So the internet is simply:

Client → Request → Server → Response → Client

Why Do We Need to Talk to Servers?

As developers, we constantly need to:

• Fetch data

• Send data

• Test APIs

• Debug backend logic

• Check if a server is alive

Browsers do this for users.
Developers need tools that show what is actually happening.

That’s where cURL comes in.

cURL is a tool that lets you talk to a server from the terminal.

No browser.
No UI.
No buttons.

Browser: Friendly, hides complexity
cURL: Honest, shows everything

You type a command, cURL sends a request, and the server’s response is printed as raw text.

Why programmers need cURL

Programmers use cURL because it helps them:

• Test APIs without frontend

• Debug backend issues

• Understand HTTP deeply

• Check server responses

• Automate requests in scripts

• Learn how real client-server communication works

• Works everywhere (Linux, macOS, Windows)

Real-world uses:

• “Is my API alive?”

• “Why is this endpoint failing?”

• “What exactly is the server returning?”

• “Does authentication work?”

Behind the scenes

First, cURL sends a request to the server.
The server reads the request and understands what data is needed.

After that, the server sends a response back to the client.
The response contains structured information in JSON format.

cURL prints this response directly in the terminal.

What happened?

1. cURL sent a request to example.com

2. The server received it

3. The server sent back data

4. cURL printed the response in your terminal

Usually, you’ll see:

• HTML if it’s a website

• JSON if it’s an API

Understanding Request and Response

Everything on the web works on this pair.

The Request

A request answers:

• Where are we going?

• What do we want?

When you write:

curl https://example.com

You’re saying:

“Hey server, send me your default data.”

This is called a GET request.

The Response

A response contains:

• Status → Did it work?

• Data → What did the server send?

Common ideas:

• 200 OK → Success

• 404 Not Found → Resource doesn’t exist

• 500 Server Error → Something broke inside the server

By default, cURL shows the data, not the status.

Browser Request vs cURL Request

When you use a browser:

Browser → Server → Response → Rendered webpage

When you use cURL:

cURL → Server → Response → Raw text

Same server. Same protocol. Different presentation.

Browser is for users.
cURL is for developers.

Using cURL to Talk to APIs

APIs usually return JSON, not HTML.

Try:

curl https://api.github.com

You’ll see:

• Raw JSON

• Exactly what the server sends

• No formatting tricks

This is how:

• Frontends talk to backends

• Services talk to each other

• Microservices communicate

cURL lets you see that communication directly.

Introducing GET and POST

We keep it simple.

GET → Asking for data

curl https://api.example.com/users

Meaning:

“Give me users.”

Used for:

• Fetching data

• Reading resources

POST → Sending data

curl -X POST https://api.example.com/users

Meaning:

“I want to send something to you.”

For now, don’t worry about sending actual data.
Just understand the concept:

Where cURL Fits in Backend Development

Before frontend exists:

• Use cURL to test endpoints

When bugs appear:

• Use cURL to isolate issues

When authentication fails:

• Use cURL to verify tokens

When APIs break:

• cURL is the first tool engineers use

cURL sits between:

Backend logic and real-world communication

Common Mistakes Beginners Make with cURL

❌ cURL shows raw data, not visuals.

❌ That raw output is clarity, not chaos.

❌ Using too many flags too early
❌ Thinking cURL is outdated

Important cURL Flags (Only the Useful Ones)

Keep these in mind. You don’t need all of them immediately.