Skip to content
Postman API Testing Tips

How To Use Postman To Send Data

API Testing Blog

How to Use Postman to Send Data for API Testing

Postman is a powerful tool for API testing, and one of its key features is the ability to send data to your API endpoints. This guide will cover the essentials of using Postman for data sending, with practical examples and step-by-step instructions.

1. Understanding the Basics: Request Types and Data Formats

Before sending data, it’s important to understand the fundamental concepts of HTTP requests and data formats:

HTTP Request Methods:

  • GET: Retrieves data from a server.
  • POST: Sends data to a server to create or update a resource.
  • PUT: Completely replaces an existing resource with new data.
  • PATCH: Modifies specific parts of an existing resource.
  • DELETE: Removes a resource from the server.

Data Formats:

  • JSON (JavaScript Object Notation): Human-readable format used extensively in web APIs.
  • XML (Extensible Markup Language): Structured data format widely used for data exchange.
  • FormData: Used for uploading files or sending data in key-value pairs.

2. Creating a New Request: Sending Data with POST

Let’s start with a simple example using the POST method to send data to a fictional user registration API.

Step 1: Create a New Request:

  1. Open Postman and click the “New” button to create a new request.

Step 2: Define the Request:

  1. Method: Select “POST” from the dropdown.
  2. URL: Enter the API endpoint URL. For example, https://example.com/api/users.
  3. Headers:
    • Content-Type: Set this to application/json for sending data in JSON format.
    • Authorization: Include any authentication headers if required.

Step 3: Send the Data (JSON):

  1. Switch to the “Body” tab.
  2. Select “raw” and choose “JSON” from the dropdown.
  3. Paste the following JSON data:
{
    "firstName": "John",
    "lastName": "Doe",
    "email": "john.doe@example.com",
    "password": "P@sswOrd1"
}

Step 4: Send the Request:

  1. Click the “Send” button.

Result: The response from the server should contain information about the newly created user.

3. Sending Data with PUT: Updating Existing Resources

Let’s update our fictional user’s email address:

Step 1: Create a new request (PUT)

  1. Similar to the previous example, create a new request but select the PUT method.
  2. URL: Update the URL to include the user’s ID, e.g., https://example.com/api/users/1.

Step 2: Send the Updated Data:

  1. In the “Body” tab, paste this JSON data:
{
    "email": "updated.email@example.com"
}

Step 3: Send the Request:

  1. Click the “Send” button.

Result: The response should indicate that the user’s email address has been updated.

4. Sending Data with PATCH: Partial Updates

Similar to PUT, but allows you to modify specific parts of a resource without affecting other fields:

Step 1: Create a new request (PATCH)

  1. Follow the same steps as in the previous section, but select PATCH as your method.

Step 2: Send the Partial Data:

  1. In the “Body” tab, send only the field you want to change:
{
    "firstName": "Jane"
}

Step 3: Send the Request:

  1. Click the “Send” button.

Result: The response will indicate success if the firstName was successfully updated.

5. Sending Data with DELETE: Removing a Resource

Step 1: Create a new request (DELETE)

  1. Create a new request and select the DELETE method.
  2. URL: Include the user’s ID in the URL, e.g., https://example.com/api/users/1.

Step 2: Send the Request:

  1. Click the “Send” button.

Result: You should receive a response indicating the user with ID 1 has been deleted, or an error message if the user doesn’t exist.

6. Sending Data with FormData

This method is useful for sending files or data in key-value pairs:

Step 1: Create a new request (POST or PUT)

  1. Create a new request and select either POST (for creating a resource) or PUT (for updating).
  2. URL: Use the appropriate endpoint for your API.

Step 2: Configure FormData:

  1. Switch to the “Body” tab.
  2. Select “form-data” from the dropdown.
  3. Add key-value pairs (e.g., name, email) or upload a file.

Step 3: Send the Request:

  1. Click the “Send” button.

Result: You’ll receive a response indicating the outcome of your request (e.g., a new resource created or a resource updated).

7. Understanding Response Codes

When you send data to an API, the server will respond with a status code. The most common status codes you’ll encounter:

  • 200 OK: Indicates a successful request.
  • 201 Created: Indicates a new resource has been successfully created.
  • 204 No Content: Indicates a successful request but no content is returned.
  • 400 Bad Request: Indicates an error in the request.
  • 401 Unauthorized: Indicates that the user is not authenticated.
  • 403 Forbidden: Indicates that the user does not have permission to access the resource.
  • 404 Not Found: Indicates that the requested resource was not found.
  • 500 Internal Server Error: Indicates that there was an error on the server.

8. Advanced Techniques: Using Environments and Collections

Environments:

  • Organize multiple API endpoints: Use environments to store variables like API base URLs, authentication tokens, and other settings (e.g., different environments for development, testing, and production).

Collections:

  • Group related requests: Collections allow you to organize related requests into folders, making it easier to manage a set of API tests.

Conclusion

Postman is a versatile tool for sending data to APIs, offering a user-friendly interface and powerful features. By mastering the methods outlined in this guide, you can effectively test your APIs, ensuring they function as expected and deliver reliable data.

API Testing Blog