cURL for Beginners: Talk to Any Server from Your Terminal

amrit rajput — Fri, 23 Jan 2026 15:56:52 GMT

cURL: A Command-Line Tool and Library for Transferring Data with URLs

cURL is a tool that allows you to send a request to a server from your terminal and view the response.

While browsers communicate with servers using a graphical interface, cURL lets you interact with servers through the terminal in text format.

This tool also supports the use of all the following protocols: DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, and TFTP.

Example:

curl https://example.com

This sends a request to the server and prints the response (HTML/JSON/text).

Why programmers use it:

Test APIs quickly

Check if an API endpoint is working
Get data in JSON format instantly

Debug backend issues

See status codes like 200, 404, 500
Understand why a request is failing

Send requests without a frontend

Backend can be tested even if the frontend is not built yet

Check server response clearly

You can view response headers + body
Helps in troubleshooting authentication, CORS, etc.

Automate API calls

Useful in scripts, CI/CD, testing, and deployments

First cURL Command: Testing a Website in Seconds:

Meaning of output:

301 Moved
That means Google is redirecting you from:

https://google.com → https://www.google.com/

Example

curl.exe -L https://google.com

Output (trimmed):


"en-IN">

  "UTF-8">
  Google


  ...

Note: Output is trimmed for readability.

1. GET (Fetch data)

Get all posts

curl.exe https://jsonplaceholder.typicode.com/posts

Get a single post

curl.exe https://jsonplaceholder.typicode.com/posts/1

2.POST (Create new data)

curl.exe -X POST https://jsonplaceholder.typicode.com/posts ^
  -H "Content-Type: application/json" ^
  -d "{\"title\":\"hello\",\"body\":\"first post\",\"userId\":1}"

-d = data you are sending
Content-Type tells server it’s JSON

3.PUT (Replace full data)

PUT usually means replace the entire object.

curl.exe -X PUT https://jsonplaceholder.typicode.com/posts/1 ^
  -H "Content-Type: application/json" ^
  -d "{\"id\":1,\"title\":\"updated title\",\"body\":\"updated body\",\"userId\":1}"

4. PATCH (Update only some fields)

PATCH means partial update.

curl.exe -X PATCH https://jsonplaceholder.typicode.com/posts/1 ^
  -H "Content-Type: application/json" ^
  -d "{\"title\":\"only title updated\"}"

5.Send Headers (Authorization / Token / etc.)

Example with a custom header:

curl.exe https://jsonplaceholder.typicode.com/posts/1 ^
  -H "Accept: application/json" ^
  -H "X-My-App: test"

Authorization header example (very common in real APIs)

curl.exe https://api.example.com/profile ^
  -H "Authorization: Bearer YOUR_TOKEN"

6. See Response Headers + Status Code

Show headers + body

curl.exe -i https://jsonplaceholder.typicode.com/posts/1

Only headers (no body)

curl.exe -I https://jsonplaceholder.typicode.com/posts/1

7. Save Response to a File

Save JSON output to a file

curl.exe https://jsonplaceholder.typicode.com/posts -o posts.json

Common Mistakes Beginners Make with cURL

Using curl in PowerShell instead of curl.exe
Forgetting https:// in the URL
Not following redirects (301/302) → missing -L
Confusing GET and POST
Sending JSON without Content-Type: application/json
Writing wrong JSON format / escaping issues
Expecting a browser-like UI output (cURL shows raw data)
Not checking status codes and headers (missing -i)
Hitting the wrong endpoint / missing slash /
Copy-pasting Linux/mac commands directly into Windows (line breaks issue)

Conclusion:

cURL is a command-line tool used to send requests to servers and APIs directly from the terminal. It helps programmers test and debug backend endpoints quickly by checking the response data, status codes (like 200, 404), and headers. With cURL, you can perform basic HTTP operations like GET (fetch data) and POST (send data) without needing a browser or frontend, making it a fast and powerful tool for API testing and backend development.

cURL: Talk to Server from Your Terminal