Postman

Postman

Testing API endpoints from a browser only works for GET requests. To test POST, PUT, and DELETE, you need a dedicated tool. Postman is the industry-standard API testing tool that lets you send any type of HTTP request, set headers, include JSON bodies, and inspect responses.

What Is Postman?

Postman is a free application for building, testing, and documenting APIs. It provides a graphical interface for crafting HTTP requests — much easier than using the command line or writing test scripts.

Installing Postman

Download Postman from postman.com and install it. You can also use the web version at web.postman.co. A free account is optional but recommended for saving your requests.

The Postman Interface

Section	Purpose
Method dropdown	Select GET, POST, PUT, DELETE, PATCH, etc.
URL bar	Enter the endpoint URL (e.g., http://localhost:3000/api/ninjas)
Params tab	Add query string parameters
Headers tab	Set request headers (Content-Type, Authorization, etc.)
Body tab	Add request body data (JSON, form data, etc.)
Response panel	Shows the server response (body, status code, headers, time)

Sending a GET Request

Method: GET
URL: http://localhost:3000/api/ninjas
Click "Send"

The response panel shows the JSON data returned by your server, the status code (200 OK), and the response time in milliseconds.

Sending a POST Request with JSON Body

Method: POST
URL: http://localhost:3000/api/ninjas

Body tab:
  → Select "raw"
  → Select "JSON" from the dropdown
  → Enter:
{
    "name": "Ryu",
    "rank": 5,
    "available": true
}

Click "Send"

Postman automatically sets the Content-Type: application/json header when you select JSON as the body format.

Testing All CRUD Operations

Operation	Method	URL	Body
Get all	GET	/api/ninjas	None
Get one	GET	/api/ninjas/123	None
Create	POST	/api/ninjas	JSON object
Update	PUT	/api/ninjas/123	JSON object
Delete	DELETE	/api/ninjas/123	None

Organizing with Collections

Postman collections let you group related requests together. Create a collection called "REST API" and add all your ninja endpoint requests to it. Collections can be shared, exported, and documented.

Environment Variables

// Instead of hardcoding:
http://localhost:3000/api/ninjas

// Use a variable:
{{base_url}}/api/ninjas

// Where base_url = http://localhost:3000

Environment variables let you switch between local development and production URLs without editing every request. Create environments for "Development" and "Production" with different base_url values.

Alternative: cURL

# GET request
curl http://localhost:3000/api/ninjas

# POST request with JSON body
curl -X POST http://localhost:3000/api/ninjas \
  -H "Content-Type: application/json" \
  -d '{"name":"Ryu","rank":5}'

# DELETE request
curl -X DELETE http://localhost:3000/api/ninjas/123

cURL is a command-line tool that comes pre-installed on most systems. It is useful for quick tests but Postman is more convenient for complex requests and ongoing development.

Key Takeaways

• Postman lets you test all HTTP methods — not just GET (which is all a browser can do from the URL bar)
• Select the method, enter the URL, set the body (for POST/PUT), and click Send
• For JSON bodies, select "raw" → "JSON" in the Body tab
• Collections organize related requests; environment variables handle different server URLs
• The response panel shows the body, status code, headers, and response time