Getting Started with Postman

Postman is the most popular tool for API testing. It lets you send requests, inspect responses, write assertions, and automate test suites — all without writing a single line of backend code.

Installing Postman

Download Postman from postman.com. It's available for Windows, macOS, and Linux. There's also a web version, but the desktop app is recommended for full functionality.

Your First Request

1. Open Postman and click New → HTTP Request
2. Set the method to GET
3. Enter the URL: https://jsonplaceholder.typicode.com/posts/1
4. Click Send

You should see a JSON response:

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati...",
  "body": "quia et suscipit\nsuscipit recusandae..."
}

Congratulations — you just tested an API!

Understanding the Postman Interface

Request Area

• Method selector: GET, POST, PUT, PATCH, DELETE
• URL bar: Where you enter the endpoint
• Params tab: Add query parameters
• Headers tab: Add custom headers
• Body tab: Send JSON, form data, or raw text
• Auth tab: Configure authentication

Response Area

• Body: The response data (JSON, HTML, XML)
• Headers: Response headers from the server
• Status: HTTP status code and time
• Size: Response size in bytes

Collections

Collections are folders that organize related requests. Think of them as test suites.

Creating a collection:

1. Click Collections in the sidebar
2. Click + New Collection
3. Name it "JSONPlaceholder API"
4. Add requests by clicking Add Request

Example collection structure:

📁 JSONPlaceholder API
  📁 Posts
    GET List all posts
    GET Get single post
    POST Create post
    PUT Update post
    DELETE Delete post
  📁 Users
    GET List all users
    GET Get single user

Environments

Environments let you switch between different servers (dev, staging, production) without changing your requests.

Creating an environment:

1. Click Environments in the sidebar
2. Click + New Environment
3. Name it "Development"
4. Add a variable:
   • Variable: base_url
   • Value: https://jsonplaceholder.typicode.com

Using environment variables: Replace hardcoded URLs in your requests:

Before: https://jsonplaceholder.typicode.com/posts
After:  {{base_url}}/posts

Now you can switch to a "Staging" environment with a different base_url and all your requests update automatically.

Variables

Postman supports multiple variable scopes:

Variable syntax: {{variable_name}}

Sending POST Requests

To create a resource:

1. Set method to POST
2. Enter URL: {{base_url}}/posts
3. Go to Body tab
4. Select raw and JSON
5. Enter:

{
  "title": "My Test Post",
  "body": "This is a test.",
  "userId": 1
}

6. Click Send
7. Verify the response is 201 Created with the new resource

Importing and Exporting

Collections can be shared with your team:

• Export: Right-click a collection → Export → Save as JSON
• Import: Click Import → Upload the JSON file
• Share: Use Postman workspaces for real-time collaboration