Capturing API Calls from Mobile Apps Using Fiddler

To use Fiddler for capturing API calls from mobile apps, follow these steps:

Step 1: Install Fiddler

• Download Fiddler: Go to the Fiddler website and download the latest version for your operating system.
• Install Fiddler: Follow the installation instructions provided.

Step 2: Configure Fiddler as a Proxy

• Open Fiddler.
• Check Proxy Settings: By default, Fiddler listens on port 8888. You can check or change this in Tools > Options > Connections.
• Allow Remote Connections: Make sure "Allow remote computers to connect" is checked if you’re using a physical device.

Step 3: Find Your Computer’s IP Address

• Open Command Prompt (Windows) or Terminal (macOS/Linux).
• Run ipconfig (Windows) or ifconfig (macOS/Linux) to find your local IP address (something like 192.168.1.x).

Step 4: Configure Your Mobile Device

• Connect to the Same Network: Ensure your mobile device is on the same Wi-Fi network as your computer.
• Set Up Proxy on Mobile:
  • For Android:
    1. Go to Settings > Network & internet > Wi-Fi.
    2. Long press on your connected network and select Modify network.
    3. Expand advanced options and set Proxy to "Manual".
    4. Enter your computer’s IP address and port 8888.
  • For iOS:
    1. Go to Settings > Wi-Fi.
    2. Tap the info icon (i) next to your connected network.
    3. Scroll to HTTP Proxy, select Manual.
    4. Enter your computer’s IP address and port 8888.

Step 5: Capture Traffic in Fiddler

• Open the Mobile App: Start using the app on your mobile device.
• View Traffic in Fiddler: You should see the network requests being captured in Fiddler’s main window.

Step 6: Analyze Requests

• Click on any request in Fiddler to see details such as:
  • Request URL
  • Request Method (GET, POST, etc.)
  • Headers
  • Request Body (for POST requests)
  • Response Body and status codes

Step 7: Configure SSL Decryption (if needed)

• If the app uses HTTPS, you may need to set up SSL decryption:
  • Enable HTTPS Decryption: Go to Tools > Options > HTTPS and check Decrypt HTTPS traffic.
  • Install the Fiddler Root Certificate: Follow the prompts to install the certificate on your mobile device. You may need to trust this certificate in your device settings.

Troubleshooting Tips

• Firewall Settings: Ensure your firewall is not blocking Fiddler or the required ports.
• Proxy Settings: Double-check the IP address and port number in your mobile device's proxy settings.
• Restart Devices: Restart both your mobile device and Fiddler if you encounter issues.

Summary

By following these steps, you can effectively capture and analyze API calls made by mobile apps using Fiddler. This tool allows developers to monitor network traffic, troubleshoot issues, and ensure that API interactions are functioning as expected.

Conclusion

Using Fiddler for capturing API calls from mobile applications is a powerful method for debugging and optimizing your app's performance. By configuring your mobile device correctly and analyzing the captured traffic, you can enhance the quality of your application and improve user experience.  

 

 #APITesting, #Fiddler, #ProxySetup, #MobileDevelopment, #NetworkTraffic, #Debugging, #SoftwareTesting, #DevelopmentTools, #Android, #iOS