Skip to content
Postman API Testing Tips

How To Use Postman Interceptor Chrome Extension

API Testing Blog

Postman Interceptor Chrome Extension: A Comprehensive Guide for API Testing

The Postman Interceptor Chrome extension empowers you to capture and modify HTTP requests made by your browser, making it a powerful tool for API testing. This guide will walk you through its various functionalities, providing practical examples and step-by-step instructions for effective API testing.

Installation and Setup

  1. Install Postman Interceptor: Open the Chrome Web Store and search for “Postman Interceptor.” Click “Add to Chrome” to install the extension.
  2. Enable the Interceptor: Once installed, you’ll find the Postman Interceptor icon in your Chrome extensions bar. Click the icon to enable the interceptor.
  3. Access Postman: Open Postman and navigate to the “Interceptor” tab. This is where you’ll manage captured requests and set up rules.

Capturing Requests

  1. Start Browsing: The Interceptor automatically begins capturing HTTP requests made by your browser.
  2. View Captures: In the Postman Interceptor tab, you’ll see a list of captured requests. Each entry displays the request method (GET, POST, etc.), URL, and status.
  3. Filter Requests: Use the “Filter” field to narrow down captures based on keywords like the URL or request method.
  4. Inspect Requests: Click on any captured request to view its details, including headers, body, and response.

Modifying Requests and Responses

Modifying Request Headers

  1. Select Request: Click on the captured request you want to modify.
  2. Edit Headers: In the “Headers” tab, you can add, edit, or remove headers.
  3. Send Modified Request: Click the “Send” button to send the modified request.

Modifying Request Body

  1. Select Request: Click on the captured request you want to modify.
  2. Edit Body: Choose the appropriate body format (e.g., JSON, XML) and modify the body content as required.
  3. Send Modified Request: Click the “Send” button to send the modified request.

Modifying Response Body

  1. Select Request: Click on the captured request you want to modify.
  2. Mock Responses: Go to the “Mock Response” tab. You can create and save mock responses, which the Interceptor will use when it intercepts and sends the request.
  3. Edit Responses: Choose the appropriate body format and modify the mock response content.
  4. Save Mock Responses: Click “Save” to keep your mock responses available for future modifications.

Creating Rules for Automated Testing

Rules allow you to automate common API testing scenarios.

Creating a Rule

  1. Go to the Rules Tab: In the Postman Interceptor tab, click “Rules.”
  2. Create a New Rule: Click the “Add Rule” button.
  3. Configure Rule: Input the following details:
    • Match: Configure the conditions for matching requests based on URL, method, headers, or body content. Here is a sample code snippet:
    { "url": "https://api.example.com/users", "method": "GET" }
    • Action: Define the action to take when a request matches the rule. This could be:
      • Modifying Request: Change headers, body, or query parameters.
      • Mocking Response: Replace the actual API response with a custom response.
    • Name: Give your rule a descriptive name.

Example: Mocking a Response

Let’s say you want to test an API endpoint that requires specific authentication headers. Using Postman Interceptor, you can create a rule to mock the authentication response and avoid actually interacting with the real API during testing.

  1. Create a Rule: Name the rule “Mock Authentication”.

  2. Match: Define the rule to match requests to the target API endpoint (e.g., “https://api.example.com/auth/login”).

  3. Action: Choose “Mock Response.”

  4. Mock Response Body: Enter the following sample code to mock a successful authentication response:

    {
        "token": "your_mock_token",
        "user": {
            "id": 1,
            "email": "test@example.com"
        }
    }

  5. Save Rule: Click “Save Rule” to complete the setup.

Applying Rules

Once defined, your rules automatically apply to intercepted requests matching the defined criteria. You can view the applied rule status in the “Rules” tab of Postman Interceptor.

Conclusion

The Postman Interceptor Chrome extension offers a powerful set of features for API testing and debugging, allowing you to capture, modify, and control HTTP requests made by your browser. Mastering these techniques enhances your testing capabilities and simplifies the process of verifying API functionalities.

API Testing Blog