Skip to content
Postman API Testing Tips

How To Use Postman For Api Post Request

API Testing Blog

Mastering API POST Requests with Postman: A Step-by-Step Guide

Postman is a powerful tool for interacting with APIs, making it an invaluable asset for API testing and development. While GET requests retrieve data, POST requests are used to send data to the server, often for creating new resources. This guide will walk you through the process of using Postman for API POST requests, covering various scenarios and providing practical examples.

1. Setting Up Your POST Request

  • Open Postman: Launch the Postman application. You can use the desktop app or the browser version.
  • Create a New Request: Click on the “New” button to create a new request. You’ll be presented with a blank request window.
  • Select ‘POST’ Method: Choose the “POST” method from the dropdown menu next to the request URL. This indicates that you want to send data to the server.

2. Specifying the Target URL

The URL you enter here is the endpoint you want to interact with. This endpoint will typically be provided by the API documentation.

Example: For a hypothetical API managing user accounts, your URL might look like: https://api.example.com/users.

3. Defining Your Request Body: The Heart of the POST Request

The request body is where you specify the data you want to send to the server.

a) Using JSON:

JSON (JavaScript Object Notation) is the most common format for API data exchange. Postman allows you to effortlessly format your data as JSON.

  • Click on the ‘Body’ tab: This will reveal options for defining the body content.
  • Select “raw” and JSON: Choose “raw” for raw text input, and select “JSON” as the type.
  • Enter Your JSON Data: Compose your data in valid JSON format.

Example:

{
  "firstName": "John",
  "lastName": "Doe",
  "email": "john.doe@example.com"
}

b) Working with Form Data: For sending data as form parameters, select “form-data” in the “Body” tab. Each parameter is entered as a key-value pair.

Example:

key: firstName
value: John
key: lastName
value: Doe
key: email
value: john.doe@example.com

4. Adding Headers for Context

Headers provide additional information about the request. Common headers include:

  • Content-Type: Indicates the data format of the request body. For JSON, set it to application/json.
  • Authorization: If the API requires authentication, use this header to send your credentials.

Example:

Content-Type: application/json
Authorization: Bearer <your_access_token>

5. Requesting and Inspecting the Response

  • Send Request: Click the “Send” button to execute your POST request.
  • Reviewing the Response: Postman will display the server’s response in different tabs:
    • Body: Shows the response data (often in JSON).
    • Headers: Displays headers sent back from the server.
    • Status Code: Indicates the success or failure of the request.
    • Cookies: Contains any cookies sent with the response (relevant for session handling).

Example: A successful API POST request might return a 201 (Created) status code along with a JSON object representing the newly created resource.

6. Example: Creating a New User With Postman

Let’s assume we want to create a new user via a user management API:

  1. Create a POST request:
    • URL: https://api.example.com/users
    • Body:
    {
      "firstName": "Jane",
      "lastName": "Smith",
      "email": "jane.smith@example.com"
    }
    • Headers:
    Content-Type: application/json
  2. Send the request.
  3. Inspect the response: You should see a 201 (Created) status code and a JSON object containing the newly created user’s data in the response body.

7. Utilizing Postman Collections: Organizing Your Workflows

Postman Collections provide a structured way to group your API requests. You can then easily share, run, and test these collections.

  • Creating a Collection: Click the “New” button and select “Collection”.
  • Adding Requests: Drag and drop your individual POST (or any other type) requests into the collection.
  • Running Collections: Use the “Run” button to execute all requests in a collection, allowing you to test a series of API interactions.

8. Leveraging Environments for Flexibility

Postman environments allow you to define variables that can be used in your API requests. This is particularly helpful when:

  • Working on Multiple Environments: You can have separate environments for development, testing, and production, each with different endpoint URLs.
  • Storing Sensitive Information: Environments can store API keys, tokens, and other sensitive information securely, keeping them separate from your actual requests.

Example:

Environment:

key: apiEndpoint
value: https://api.example.com/users

Request URL: {{apiEndpoint}}

With this environment, you can easily switch between different API endpoints by changing the environment, without modifying your requests manually.

9. Testing and Validating Your API POST Requests: Ensuring Accuracy

Postman provides powerful tools for testing and validating your API interactions:

  • Assertions: Verify specific aspects of your responses, such as status codes, headers, or content.
  • Tests: Write custom JavaScript code to further validate your responses and perform complex checks.
  • Pre-request scripts: Define code that runs before each request, allowing for dynamic data generation or other actions.

Example: Assertions

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


pm.test("Response body contains firstName", function () {
  pm.expect(pm.response.json().firstName).to.be.equal("Jane");
});

By incorporating tests and assertions, you enhance the reliability of your API testing and ensure the accurate functioning of your API features.

Conclusion: Postman’s Role in API Testing

Postman’s intuitive interface, robust features, and extensive documentation make it a top choice for API testing. It enables you to:

  • Build and send complex POST requests.
  • Manage your API interactions efficiently with collections.
  • Store sensitive data securely using environments.
  • Validate your API behavior with automated testing and assertions.

Postman empowers you to thoroughly test your APIs before deployment, ensuring their robustness and reliability.

API Testing Blog