Debugging Network Requests in Swift: A Complete Guide

When building iOS apps that depend on remote APIs, debugging network requests in Swift becomes an essential skill. Without the ability to inspect and troubleshoot network calls, developers can quickly become stuck trying to understand why data isn’t loading or responses are failing. Whether you’re working with URLSession, third-party libraries like Alamofire, or even custom networking layers, this guide will help you master the fundamentals and tools required to debug network traffic efficiently.

Why Debugging Network Requests Matters

Most modern apps rely on RESTful APIs, GraphQL, or other remote services. But the path between request and response can be unpredictable. You might encounter:

• No response from the server
• Malformed or unexpected data
• Incorrect HTTP headers
• Authentication issues
• Network timeouts

Debugging these issues requires both Swift code-level tools and broader debugging strategies.

Built-in Tools for Debugging

1. Using print() Statements in Swift

For beginners, inserting print() statements directly after receiving data or before sending requests helps track what’s going out and coming in.

Example:

print("Sending request to: \(request.url?.absoluteString ?? "Unknown URL")")
print("Received data: \(String(data: data, encoding: .utf8) ?? "No data")")

2. URLSession Task Debugging

If you’re using native URLSession, you can attach custom completion handlers to log the response, data, and error:

let task = URLSession.shared.dataTask(with: request) { data, response, error in
    if let error = error {
        print("Error: \(error.localizedDescription)")
    }
    if let response = response as? HTTPURLResponse {
        print("Status code: \(response.statusCode)")
    }
    if let data = data {
        print("Response data: \(String(data: data, encoding: .utf8) ?? "")")
    }
}

Advanced Tools for Debugging Network in Swift

1. Charles Proxy or Proxyman

These macOS tools allow you to monitor and inspect all outgoing and incoming HTTP(S) traffic from your iOS device or simulator. You can also modify requests on the fly to test how your app handles various responses.

Note: You’ll need to install SSL certificates for HTTPS inspection.

2. Xcode Network Debugger

Since Xcode 11, Apple has added a network debugging tab under the Debug Navigator (⌘+7). It shows ongoing requests, their URLs, status codes, and duration. It’s especially useful when debugging URLSession tasks.

3. Use Breakpoints

Set breakpoints inside your networking methods and use Xcode’s debugger to inspect variables, requests, and responses. Conditional breakpoints are powerful for stopping only when a specific endpoint is called.

Third-Party Tools

Alamofire Debugging

If you’re using Alamofire, enable request logging using its built-in logging features:

AF.request(url).responseJSON { response in
    debugPrint(response)
}

You can also use Alamofire’s event monitors to inspect the request lifecycle.

Best Practices for Network Debugging in Swift

1. Log Requests in Development Mode Only
   Use compile-time flags like #if DEBUG to log network traffic only in development builds.
2. Implement a Network Logger
   Create a central logging class to print or store request/response logs for future analysis.
3. Handle All HTTP Status Codes Gracefully
   Map status codes to user-friendly error messages to make debugging easier for QA and users.

External Tool Recommendation

For more advanced inspection, consider using Proxyman. It offers a beautiful interface, native Apple Silicon support, and works well with iOS devices and simulators.

Conclusion

Debugging network requests in Swift involves a mix of logging, tooling, and smart breakpoints. Mastering these techniques saves hours of frustration and leads to better, more reliable apps. Whether you use native tools or third-party solutions, make sure your debugging workflow is part of your daily development process.