How to Run Postman and Check API — Step-by-Step Guide for Beginners

If you’ve ever heard about APIs and wondered how developers actually “test” them, then this tutorial is for you. Today, I’ll show you how to install and use Postman, one of the most popular tools for checking APIs. I’ll explain it in a very simple way, so even if you’re not from a technical background, you’ll understand everything clearly.

🌟 What Is Postman?

Postman is a free tool that allows you to send requests to an API and check the responses. In simple words, it’s like a messenger between your computer and the server — you send something, and the server replies. Postman helps you understand what’s happening behind the scenes.

Easy to use, even for beginners
Works on Windows, macOS, and Linux
Useful for developers, testers, and students

🧰 Step 1: Download and Install Postman

First, go to the official Postman website: https://www.postman.com/downloads/

Choose your operating system (Windows, Mac, or Linux).
Download the installer.
Install it just like you install any other software.
Open Postman after installation is complete.

💡 Tip: You can also use Postman directly in your browser without installing — just create a free account on their website.

🔑 Step 2: Understand the Basic Interface

When you open Postman, you’ll see a simple interface with these main sections:

Request Type (GET, POST, PUT, DELETE)
Request URL (Where you send your request)
Params, Headers, Body (Where you enter additional data)
Send Button (To make the request)
Response Section (Where you see the result)

I personally love how clean and simple it is. You don’t need to be a coding expert to use it.

🚀 Step 3: How to Check an API

Let’s say we want to check a sample API. You can use this free one for practice:

https://jsonplaceholder.typicode.com/posts

Open Postman.
Select GET as the request type.
Paste the above URL into the request URL box.
Click the Send button.

✅ You’ll instantly see a response in JSON format. This means the API is working perfectly. This is how I first learned API testing — and trust me, it’s quite fun when you see real data coming from the server!

📬 Step 4: Testing POST API (Sending Data)

GET is for getting data, but POST is for sending data. Here’s how you can test it:

Change the request type to POST.
Use the same URL: https://jsonplaceholder.typicode.com/posts
Click on Body → Select raw → Choose JSON.

Paste this sample JSON:

{
  "title": "My First API Post",
  "body": "Learning Postman is easy!",
  "userId": 1
}

Click Send.

🎉 You should get a response back with an ID. This means your POST request worked successfully.

🧠 Step 5: Understanding API Responses

When you send a request, the server replies with something called a status code:

200 OK — Everything is good.
201 Created — Your data was added successfully.
400 Bad Request — Something is wrong with your request.
404 Not Found — The API URL is incorrect.
500 Server Error — The server has an issue.

I usually keep an eye on this status code first because it tells me whether the issue is on my side or the server’s side.

🛡️ Step 6: Using Headers and Authentication (Optional)

Some APIs require extra security. You may need to add API keys or tokens. In Postman:

Click on Headers.
Add something like:
- Key: Authorization
- Value: Bearer YOUR_API_KEY

This is common in real-world projects like payment gateways, social media APIs, and more.

📊 Step 7: Save Your API Requests

When working on multiple projects, I recommend saving your requests inside Collections. This way, you don’t need to type them again and again.

Click on Save.
Give it a name (e.g., “My API Test”).
Add it to a collection.

This has helped me stay organized and faster while testing.

⚡ Step 8: Bonus — Automate with Collections Runner

Postman also has a cool feature called Collection Runner, where you can run multiple requests automatically. This is useful if you want to test 10 or 20 endpoints at once.

You can even create environment variables to make testing more flexible. For example, instead of typing the base URL every time, you can store it in a variable.

📝 Final Thoughts

Using Postman is one of the easiest ways to start learning APIs. Even if you’re a beginner, once you test a few APIs, you’ll understand how websites and apps talk to servers. When I first started, I used to test random APIs daily — and slowly, I got confident enough to use them in my projects.