What Tools Help Me Find Problems in My App Code?

Every app developer spends a surprising amount of their time finding and fixing problems in their code, which makes having the right set of tools absolutely necessary for building something that actually works properly.

Finding bugs in your code is like finding tiny cracks in a building before they turn into bigger structural problems that affect real users

I've been building mobile apps for ten years now and the way we find problems has changed completely. The early days were much harder because we had to guess where things were going wrong (usually by adding loads of print statements throughout our code and hoping we'd spot the issue). These days the tools available can tell you exactly what line of code caused a crash, how much battery your app is using, and even which API call is making your app run slowly.

The difference between a developer who knows their debugging tools and one who doesn't is probably about three hours per bug. That adds up fast. When you're working on a healthcare app where a crash could mean someone misses their medication reminder, or a fintech app where a calculation error could cost users real money, having proper debugging tools isn't optional anymore.

Understanding Why Debugging Tools Matter

The fact is that every app has bugs, even the ones that seem to work perfectly. I've worked on apps that passed all our internal testing but still crashed for specific users who had unusual phone settings or older device models we didn't think to check. One e-commerce app we built worked fine for weeks until a user in Manchester tried to use it with their screen reader enabled and discovered that half the buttons didn't announce themselves properly.

Users delete apps quickly.

If your app crashes twice, you've probably lost that user forever. The research shows that 62% of users will uninstall an app if they experience bugs or crashes within the first few days of downloading it, and each one of those lost users cost you anywhere from £3 to £8 in acquisition costs depending on your marketing channel.

Debugging tools help you catch problems before users see them, and when problems do slip through (because they always do), these tools help you fix them within hours instead of days. The financial side matters too because every hour spent hunting for a bug without proper tools is an hour you're paying a developer (probably £40-70 per hour for a decent mobile developer) to essentially work blind.

• Reduce time spent finding the root cause of issues
• Catch performance problems before they affect user experience
• Track down bugs that only happen on specific devices or OS versions
• Monitor real-world app behaviour after release
• Prevent small issues from becoming expensive problems

Built-In Debug Options in Your Development Environment

Your development environment (whether that's Xcode for iOS or Android Studio for Android development) comes with debugging features that most developers never fully use. I've watched developers struggle with bugs for hours when the solution was literally in a menu they'd never opened.

The debugger lets you pause your app whilst it's running and step through the code line by line. You can see exactly what value each variable holds at any moment, which means you can spot when something unexpected is happening. I probably use breakpoints fifty times a day at least... they're little markers you place in your code that tell the app to stop running at that exact point so you can inspect what's going on.

Set up conditional breakpoints that only trigger when specific conditions are met, like when a variable equals a certain value. This saves you from hitting the same breakpoint hundreds of times whilst waiting for the problematic scenario to occur.

The memory graph debugger (especially useful in iOS development) shows you which objects are using memory and whether you've got memory leaks. A memory leak happens when your app holds onto data it should have thrown away, which gradually makes your app slower and eventually causes crashes. I found a memory leak in a booking app once that was costing users about 15MB of RAM per booking attempt... after twenty bookings the app would just crash.

Crash Reporting and Monitoring Services

Crash reporting services like Firebase Crashlytics or Sentry automatically collect information when your app crashes for real users out in the world. This was probably the biggest change in how we work over the past decade because before these services existed, users would just delete your app and you'd never know why it crashed. Having effective code management tools alongside crash reporting creates a comprehensive debugging workflow that helps you track issues across different versions.

These tools send you a full report showing exactly which line of code caused the crash, what the user was doing at the time, what type of device they were using, and even what version of the operating system they had installed. I've used Crashlytics on probably forty different apps now and it's caught bugs that we never would have found in our own testing.

The services are free up to a certain number of users (usually around 10,000 monthly active users before you need to pay anything). They work by including a small piece of code in your app that monitors for crashes and automatically uploads the crash data when the app next opens. The only problem is that they add about 200-500KB to your app size, which matters if you're trying to keep your download size small.

Performance Testing Tools That Actually Help

Performance problems are sneaky because your app might work fine but just feel a bit sluggish, and users will blame their phone rather than your app at first... but eventually they'll just stop using it. I've seen apps with perfect functionality fail completely because they took three seconds to load instead of one.

Your app needs to feel fast even more than it needs to be fast, because users judge performance based on how responsive the interface feels in their hands

Xcode Instruments (for iOS) and Android Profiler are built into your development tools and they measure things like CPU usage, memory consumption, battery drain, and network activity. The first time you profile your app properly you'll probably be shocked at what you find. I remember testing an educational app we'd built and discovering that one animation was using 80% of the CPU just to make a button fade in slightly.

Frame rate monitoring shows you whether your app is running at 60 frames per second (which feels smooth) or dropping frames (which feels janky). Battery profiling is massive now because users will absolutely delete apps that drain their battery. We built a tracking app once that worked beautifully but was checking the GPS location every five seconds even when the app was in the background... the battery drain was terrible until we changed it to only check when actually needed.

Code Quality Checkers and Automated Testing

Code quality tools scan your entire codebase looking for potential problems before they become actual problems. Things like unused variables, deprecated functions, security vulnerabilities, or code that's unnecessarily complicated. ESLint for React Native projects or SwiftLint for iOS apps will highlight issues right in your code editor as you type.

These tools enforce consistent coding standards across your team too. When you've got four developers working on the same app, having automated checks means everyone's code looks and works similarly, which makes it easier to spot problems and hand work between team members.

Automated tests are different because they actually run your code and check whether it does what you expect. Unit tests check individual functions work correctly, integration tests check that different parts of your app work together properly, and UI tests simulate user interactions to make sure the interface responds correctly. Writing tests takes time upfront (probably adds 20-30% to development time) but I've seen it save weeks of debugging time on larger projects.

The apps that need automated testing most are ones with complicated logic (like calculation engines for financial apps) or ones where bugs could cause real harm (healthcare apps, payment systems). An educational app we maintain has over 300 automated tests that run every time we make changes... they take about eight minutes to run but they've caught probably two dozen bugs that would have made it to users otherwise.

Network Debugging for API Issues

Most modern apps talk to servers through APIs to fetch data or save information, and a massive percentage of bugs happen in that communication layer. The app might be perfect but if the API returns unexpected data or times out, your app will break.

Use Charles Proxy or Proxyman to intercept and inspect all network traffic between your app and your servers. You can see exactly what data is being sent and received, modify responses to test edge cases, and simulate slow network conditions to see how your app behaves.

Network debugging tools let you see the actual HTTP requests your app sends and the responses it receives. I've used this probably a thousand times to discover that the API was returning slightly different data than we expected, or that the app was sending requests in the wrong format. One fintech app we worked on kept failing to load user transactions and we spent hours checking the app code before using Charles Proxy and discovering the server was returning dates in a different format than documented.

Testing with different network conditions matters because your users won't always have perfect wifi. The tools let you simulate 3G speeds, dropped connections, or high latency to see how your app handles poor network conditions. Does it show a helpful error message or just freeze? Does it retry failed requests or give up immediately?

Device Testing and Compatibility Tools

Your app needs to work on dozens of different devices with different screen sizes, different Android or iOS versions, and different hardware capabilities. An app that works perfectly on an iPhone 14 might crash on an iPhone 8 because of memory constraints or display oddly on an iPad because of the different screen proportions. Understanding the differences between various platforms helps you anticipate potential compatibility issues during testing.

Physical device testing is best but you can't buy fifty different phones. Cloud-based device testing services like BrowserStack or AWS Device Farm let you run your app on real devices remotely through your web browser. They're not free (plans start around £30 per month) but they give you access to hundreds of device configurations.

Emulators and simulators are faster for quick testing but they're not real devices so they'll miss some problems. I always test on at least three real devices (usually a current flagship, something mid-range from about two years ago, and an older budget device) before releasing any app update. The older budget device often reveals performance issues you'd never spot on newer hardware.

• Test on devices with different screen sizes and aspect ratios
• Check older OS versions (at least two versions back from current)
• Test with low storage space and low battery conditions
• Verify with different language settings and accessibility features enabled
• Check behaviour under different network conditions

Platform-Specific Debug Features for iOS and Android

iOS and Android each have their own debugging quirks that you need to know about. For iOS development, TestFlight lets you distribute beta versions of your app to up to 10,000 external testers before submitting to the App Store. We use this for every app we build because getting feedback from real users in real conditions catches problems that internal testing misses.

The Console app on Mac shows you real-time logs from any iOS device connected to your computer, which is brilliant for catching warnings and errors that don't cause full crashes but indicate underlying problems

Android Studio's Layout Inspector lets you see your app's entire view hierarchy whilst it's running, showing you exactly how views are nested and how much screen space each element takes up. This helped me solve a scrolling problem in an e-commerce app where invisible padding was making buttons appear cut off on smaller screens. If you're working with specialised platforms, you might also need specific development tools designed for wearable apps, which have their own unique debugging requirements.

Android's strict mode is a development setting that flashes the screen or logs warnings when your app does something potentially problematic (like writing to disk on the main thread or having memory leaks). It's deliberately aggressive to make sure you notice these issues during development rather than after launch. Battery historian for Android shows you detailed breakdowns of battery usage over time, which helped us discover that a messaging app was keeping the device awake even when no messages were being received.

Putting Your Debugging Tools to Work

The best debugging setup uses multiple tools together rather than relying on just one. I start every project by setting up crash reporting on day one (even before we have real features built) because it needs to be there when problems happen. Built-in debuggers get used daily during active development, performance profilers come out when something feels slow, and network debugging tools get opened whenever API integration doesn't work as expected. This comprehensive approach works especially well when combined with user research tools that help identify potential issues before they become bugs.

The tools themselves won't fix your bugs... they just make finding the problems faster and more reliable. You'll still need to understand your code and think through what might be causing issues, but you'll do it with actual data instead of guesses. After building apps for this long, I can tell you that the difference between projects that ship on time and ones that don't usually comes down to how quickly the team can identify and solve problems. Whether you're deciding if you need an app at all or already deep into development, having proper debugging workflows established early saves enormous amounts of time and frustration later.

If you're building an app and want help getting your debugging workflow set up properly, or if you're dealing with bugs that you can't seem to track down, get in touch with us and we'll be happy to share what we've learned from a decade of building apps across different industries.

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