Postman vs curl: A Complete Beginner’s Guide to API Testing and Automation

Introduction

You've just built a backend API, or maybe you're consuming someone else’s. Either way, testing it manually via browser is a pain. You want quick, reliable, repeatable testing. That’s where tools like Postman and curl come in.

But which one should you use? How do you even get started? This post is your go-to beginner guide—whether you're debugging your first API or automating your tenth.

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Part 1: Postman – GUI for API Testing

What is Postman?

Postman is a user-friendly desktop application for testing APIs. It supports all HTTP methods like GET, POST, PUT, DELETE and provides built-in support for test scripting, environments, mock servers, and API documentation.

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How to Install Postman

• Visit https://www.postman.com/downloads

• Download for Windows, Mac, or Linux

• Install and open the app

OR

• Open Visual Studio Code

• Go to Extensions (Ctrl + Shift + X)

• Search for "Postman" and install the official extension

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Getting Started: Your First Requests

GET Request

Method: GET
URL: https://jsonplaceholder.typicode.com/posts/1

Click Send and view the response.

POST Request

1. Set method to POST

2. URL: https://jsonplaceholder.typicode.com/posts

3. Go to Body → raw → JSON

4. Paste:

{
  "title": "Deepak",
  "body": "Learning Postman",
  "userId": 1
}

Click Send.

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Write Test Scripts in Postman

Go to the Tests tab and paste:

pm.test("Status code is 201", function () {
  pm.response.to.have.status(201);
});

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Convert to curl

• Click the </> Code button

• Choose curl

• Copy and paste it in terminal

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Part 2: curl – Command-line for Pros

What is curl?

curl stands for "Client URL". It is a lightweight command-line tool to send HTTP requests. It’s fast, scriptable, and perfect for automation in CI/CD pipelines.

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How to Install curl

Windows:

• Good news: If you're using Windows 10 (v1803 and above) or Windows 11, curl is pre-installed.

• To verify, open Command Prompt or PowerShell and run:

curl --version

If you see version details, you're ready to use curl.

For older versions or latest curl:

• Download from https://curl.se/windows

• Extract and add to your PATH if needed

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Basic curl Commands

GET Request

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

POST Request

curl -X POST https://jsonplaceholder.typicode.com/posts \
  -H "Content-Type: application/json" \
  -d '{"title":"Deepak","body":"Learning curl","userId":1}'

Add Authorization

curl -H "Authorization: Bearer YOUR_TOKEN" https://api.example.com/data

Save Response to File

curl https://api.example.com/data -o response.json

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Switching Between Postman and curl

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Postman vs curl – Feature Comparison

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When to Use What?

Use Postman if you’re exploring or debugging an API visually, or working in a team.

Use curl if you need fast, scriptable HTTP calls, or you're automating workflows.

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Alternatives to Postman and curl

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Final Thoughts

Both Postman and curl are indispensable tools for API developers. Postman is your go-to for designing, debugging, and collaborating; curl is your trusted tool for scripting, quick tests, and CI/CD pipelines.

Master both to cover all your API testing needs—from visual tools to terminal automation.