Getting Started with cURL
When we open a website, log into an app, or fetch data from an API, our computer is constantly communicating with servers over the internet.
But how does that communication actually happen?
That is where cURL becomes useful.
What Is a Server?
Before learning cURL, we first need to understand what a server is.
A server is simply a computer that stores data or services and waits for requests from other computers.
For example:
When you open YouTube, your browser sends a request to YouTube’s server.
When you log into Instagram, your app talks to Instagram’s server.
When a weather app shows temperature data, it requests information from a weather server.
Think of it like this:
Client → asks for something
Server → sends back a response
Your browser is usually the client.
Why Do We Need to Talk to Servers?
Modern applications depend heavily on server communication.
Frontend applications request:
user data
product lists
images
authentication
notifications
API responses
Backend developers constantly test APIs and servers.
Sometimes developers want to communicate with a server without opening a browser.
That is exactly why cURL exists.
What Is cURL?
cURL is a command-line tool that lets you send requests to servers directly from the terminal.
In very simple terms:
cURL is a way to send messages to servers from your terminal.
Instead of clicking buttons in a browser, you type commands.
You can:
fetch webpages
call APIs
send data
test backend servers
debug responses
Programmers use cURL because it is:
fast
lightweight
available almost everywhere
extremely useful for backend and API testing
cURL Request Flow
The flow looks like this:
You type a cURL command
cURL sends a request to a server
The server processes it
The server sends back a response
cURL displays the response in the terminal
Your First cURL Command
curl https://example.com
This is the most simplest cURL command
That’s it.
When you run this command:
cURL contacts the server
requests the webpage
prints the response in the terminal
You will see HTML content returned from the server.
Example
<!doctype html>
<html>
<head>
<title>Example Domain</title>
</head>
<body>
<h1>Example Domain</h1>
</body>
</html>
This is the server’s response.
Understanding Request and Response
Communication between client and server happens through:
Request
Response
Request
A request is what we send to the server.
Example
curl https://example.com
Here, the request means:
“Hello server, please give me this webpage.”
Response
The response is what the server sends back.
A response usually contains:
status code
headers
data/content
For example
<h1>Example Domain</h1>
This is the returned data
Basic HTTP Structure
A very simplified structure looks like this:
Request
GET / HTTP/1.1
Host: example.com
Response
HTTP/1.1 200 OK
Content-Type: text/html
Then the server sends the actual webpage data.
What Does Status Code Mean?
A status code tells us what happened.
Some common ones are
| Status Code | Meaning |
|---|---|
| 200 | Success |
| 404 | Page not found |
| 500 | Server error |
If a request works correctly, we often see:
200 OK
That means the server successfully handled the request.
Why Programmers Need cURL
Programmers use cURL constantly because it helps them test servers quickly.
Instead of building a full frontend application, they can directly test APIs from the terminal.
Common use cases:
testing backend APIs
checking server responses
debugging authentication
verifying JSON data
automating requests
learning HTTP concepts
Backend developers especially rely heavily on cURL.
Using cURL with APIs
An API allows applications to communicate with servers.
For example:
weather APIs
payment APIs
user APIs
authentication APIs
cURL is one of the easiest tools for testing APIs.
Example
curl https://jsonplaceholder.typicode.com/users
This API returns user data.
You may see something like
[
{
"id": 1,
"name": "Leanne Graham"
}
]
GET Request
The command we used earlier is a GET request.
GET means:
“Please give me some data.”
Example:
curl https://api.example.com/users
This requests user information from the server.
GET requests are mainly used for:
fetching data
reading information
loading resources
POST Request
POST is used when we want to send data to the server.
For example:
creating a user
logging in
submitting a form
Basic example:
curl -X POST https://api.example.com/users
This tells the server:
“I want to send/create something.”
At this stage, do not worry too much about extra flags or advanced options.
The goal is simply understanding that:
GET → fetch data
POST → send data
Browser vs cURL
A browser and cURL both can communicate with servers.
| Browser | cURL |
|---|---|
| Visual interface | Terminal-based |
| Renders webpages | Shows raw response |
| User-friendly | Developer-friendly |
| Designed for browsing | Designed for testing |
A browser hides many technical details.
cURL exposes them more directly.
That is why developers love it.
Where cURL Fits in Backend Development
In backend development, cURL is commonly used for:
testing APIs during development
checking server health
debugging request problems
verifying authentication systems
experimenting with endpoints
Many developers use cURL before building frontend interfaces.
Common Beginner Mistakes
When learning cURL, beginners often make a few common mistakes.
1. Forgetting the URL
Incorrect
curl
Correct:
curl https://example.com
2. Confusing GET and POST
Many beginners think every request is the same.
Remember:
GET fetches data
POST sends data
3. Expecting Beautiful Output
cURL shows raw responses.
It is not designed to look pretty like a browser.
That is normal.
