iOS Crash Reports: How to Read, Analyze, and Fix Crashes

What are iOS crash reports?

Think of an iOS crash report like the black box on an airplane, giving you vital clues whenever your app runs into problems. Understanding iOS crash reports will help you put your app back together, learn from the root cause and ensure it doesn’t happen again.

But what exactly is a crash? Well, a crash can refer to any forced termination of your app caused by an unhandled exception. In other words, anything the app can’t deal with.

So today we’ll give you a firm grasp of iOS crash reports. Not just analysing your reports after the fact, but using the in-built functionality of your crash reporting and logging tools to proactively prevent problems.

We’ll also help you identify the right iOS crash reporting tool for your business, so you’re only paying for stuff you’ll actually use.

Common reasons for iOS crashes

From reading iOS crash reports at Bugfender, we know that a big chunk of iOS crashes are caused by a small number of everyday problems. Let’s dig into those before we go any further.

Index out of range

This is a particularly common exception type. It occurs when we try to access an index on any collection that does not exist. You can easily reproduce an index out of range instance with the following code:

let array = ["1"]
print(array[2])

Force unwrapping

Using force unwrapis a rogue way to code. We’re basically telling the compiler that we’re sure an optional value isn’t nil, and it can crash if we’re wrong. Too reckless, too simplistic. Here’s a safer alternative:

var optionalValue: String? = nil
print(optionalValue!)

Dividing by zero

If we fail to put any checks into our code, it’s possible that we will come to a division and the divisor will be 0.

func divideTenBy(divisor: Int) -> Int {
	return 10 / divisor;
}
...

divideTenBy(0)

Invalid casting of types

Unrelated types are types that have no inheritance or conversion relationship. They can seriously scramble the runtime, particularly when we force out a cast to an unrelated type.

    let a = 10
        
    print(a as! String)

We’ll come back to each of these issues and give you some simple tips to stop them. For now though, let’s look at how to put some robust reporting structures in place, starting with the stack trace, the most important analytics data in our toolkit.

Part 1: How to collect crash reports and logs on ios devices

iOS crash reports from TestFlight and App Stores

If your app is in beta, TestFlight gives you crash reports from your testers. Once your app is live, you’ll get reports from real users via App Store Connect.

Both sources are super helpful for spotting bugs early – or for tracking down those annoying edge cases that only pop up in the wild.

Symbolication

Symbolication is the translation of a crash’s information from memory addresses to a more human-readable format. Want to see an example? Why sure.

Option A

Thread 0 Crashed:
0   App     0x0000000103478abc 0x103470000 + 35516
1   App     0x0000000103478f32 0x103470000 + 36658

Option B

Thread 0 Crashed:
0   App     0x0000000103478abc -[ViewController viewDidLoad] + 40
1   App     0x0000000103478f32 myScreen + 22

Which view do you prefer? It’s obviously B, right?! B gives us a clear view of where things went wrong, while A is just an unreadable stack.

How does symbolication work?

To symbolicate crashes, we need Debug Symbol (dSYM) files. These are generated in each build of our app. You can download these dSYM files from App Store Connect by going:

Your App > TestFlight tab > Choose the build you’d like to have dSYMs for > Build Metadata tab > Download dSYMs button.

Once you have your dSYM, you can symbolicate it to a more readable version.

Symbolicating a dSYM

Xcode is the preferred way to symbolicate crash reports because it uses all available dSYM files on your machine at once.

To symbolicate in Xcode, click the Device Logs button in the Devices and Simulators window, which you can access from the Windows menu button on top. Then you just need to drag and drop the crash report file into the list of device logs.

iOS crash reports from customers

Now let’s zoom in a bit more. If you have physical access to an iOS device that has crashed, you can directly access the logs on the device to unlock priceless debugging information.

Mac OS X

On Mac OS X, you can access the logs easily. First open up Xcode, then open Devices and Simulators on the Window Menu:

Here we can choose a device and drill into the device’s logs:

Now we’ve got access to the stack trace, just like we saw earlier.

Windows

Although the vast, vast majority of iOS developers will be using Macs, it is possible to build iOS apps using Windows, thanks to cross-platform technologies like Flutter, React Native and Unity.

Unfortunately, Windows can’t help us much with our debugging regime. You’ll need a Mac and Xcode to build and analyze iOS apps, and crash logs.

iPhone crash logs

As an alternative to the methods above, you can ask your users to send the iPhone crash logs to you, or get them yourself if you have access. You can also get crash reports for your beta versions through TestFlight. Otherwise, you will need an external service that collects crash data and sends it to you.

Which is where our very own Bugfender comes in…

iOS crash reports with Bugfender

Yep, we’ve got to bring our own solution to the table here. And not because we want to promote ourselves (ok, that’s kinda the reason) but Bugfender offers exactly the kind of proactive defense that we’ve been talking about.

Bugfender offers an iOS SDK that helps you go beyond default crash logs. It lets you:

• Get full device info for any crash.
• See what the user was doing right before the crash (including UI interactions).
• Capture detailed context that helps explain why things broke.

If you want more info than Apple provides by default, then Bugfender really is your friend.

But that’s enough self-promo. We’ve talked about how to get the info, now let’s look at how to read it.

Part 2: How to read iOS crash logs

At first glance, iOS crash logs can look like a big block of text. But once you get the hang of them, they’re one of the most powerful tools for tracking down bugs.

Crash log header

The top part of the crash log gives you a snapshot of what happened and where. It’s basically your crash summary.

Here’s what you’ll usually find:

• Incident Identifier. A unique ID for the crash event.
• Device Info. The model and iOS version (e.g. iPhone 13, iOS 17.6).
• App Info. The app name, bundle ID and version number.
• Process and Path. Where the app was installed and which process crashed.
• Crash Time. When the app crashed and when it was launched.
• Exception Type. The type of crash (e.g. SIGABRT, EXC_BAD_ACCESS).
• Exception Codes. Extra details like memory addresses or error codes.
• Crashed Thread. The thread that caused the crash (this is where you’ll want to look first).

Example:

Process:             MyApp [1234]
Identifier:          com.example.myapp
Version:             2.3.1 (231)
Hardware Model:      iPhone13,3
OS Version:          iOS 17.6 (Build 21G82)
Exception Type:      EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:     KERN_INVALID_ADDRESS at 0x0000000000000000
Crashed Thread:      5

Exception information

This section helps you understand the root cause of the crash. Or at least gets you close.

Here’s what to look for:

• Exception Type: The category of crash. Common ones include:
  • EXC_BAD_ACCESS: The app tried to access invalid memory (null pointers, deallocated objects etc).
  • SIGABRT: Usually comes from an uncaught exception or a failed assertion.
  • EXC_CRASH: A forced crash, often triggered on purpose (e.g. using abort()).
• Exception Codes: These are more technical, showing where the app failed at the memory level.
• Crashed Thread: This is the thread where the crash happened. Scroll down to find its backtrace.

Quick tips:

• Seeing 0x0000000000000000 usually means a null pointer was involved.
• Always symbolicate your crash logs—this turns memory addresses into readable method and file names.
• Start reading from the top of the crashed thread’s stack trace. That’s usually where things broke.

Backtraces

A backtrace is basically the same as a stack trace: us debuggers just prefer the word ‘backtrace’. This is the most crucial crash report we can obtain, because it tells us exactly what was happening when the crash unfolded.

The backtrace is a stack of method calls that shows how the app got to the crash point. Specifically, it shows us the calls that our iOS app was processing when everything went wrong. With stack traces, we can see who was calling who at the moment of the crash, and pinpoint where the execution stopped.

For example, if you take the previously given example of the invalid casting type and run an app with it, you will get something akin to:

The ViewModel.init shows exactly where we had our crash. By looking specifically at this, we can determine what was causing the unhandled exception.

Additional tip. While running your iOS app, you can check or log your stack trace at any time simply by using:

for symbol: String in Thread.callStackSymbols {
    print(symbol)
}

Part 3: How to analyze iOS crash reports

Now the final part of the tutorial – and undoubtedly the most important. We’ve talked about how to access crash reporting data, and how to understand it. Now, we need to analyze it.

It’s one thing to read a tranche of crash data. It’s another to read it with actual literacy, so we can stop the crash from happening in future. But like so many coding problems, we can break it down into step-by-step chunks.

Set the context: understand user behavior and crash environment

Before diving into the log, ask: what was the user doing when this happened? What device were they on? Which app version?

Gathering this context is key. You might find that the crash only happens on older devices, in specific regions, or during edge cases like poor network conditions. Tools like analytics platforms or custom logging really help here.

Identify patterns by grouping similar crashes

Looking at one crash log doesn’t always reveal much. But once you start grouping logs with similar stack traces or error messages, patterns start to show up.

Most crash reporting tools (including Bugfender, Crashlytics, etc.) do this for you, but it’s still good to double-check the groupings in case something subtle is getting overlooked.

Pinpoint the failure using exception and diagnostic messages

The exception type (like EXC_BAD_ACCESS) and the termination reason (if available) often point you right at the problem – whether it’s memory management, an unrecognized selector, or an issue with system resources. These lines are easy to skip, but they’re pure gold when we’re debugging.

Trace execution flow by decoding the backtrace

As mentioned, the backtrace shows us the method calls that led up to the crash point.

Start with the crashed thread. This usually shows the most direct route to the issue. Once your log is symbolicated, you’ll see actual function names instead of raw addresses. Read it from the bottom up to follow the code path your app took before crashing.

Verify your app binaries and frameworks

Sometimes the crash isn’t caused by your code directly. It might come from a third-party library or a mismatched binary. In this case, verifying your app binaries and frameworks can help by confirming that what you think is running is actually running.

Make sure your build is clean, you’ve uploaded the correct dSYM files, and you’re not mixing SDK versions in ways that could cause trouble.

Advanced analysis: dive into registers and low-level data

For hard-to-solve bugs, you may need to dive into the low-level details: registers, memory state, thread dumps, etc. It’s not fun, but it’s sometimes the only way to fix really tricky issues, especially those involving multithreading or memory corruption.

Master all that, and your crash report will look like clues, not just numbers.

Part 4: How to avoid crashes

Remember those common crash causes we mentioned at the top? Well, there’s a way we can stop them. In fact we can do more than stop them, we can prevent them.

Defensive coding means problems don’t happen, and it should be baked in to our debugging and error management regime. By putting the following steps in place, we can ensure that we’re preventing basic glitches and can focus our attention on more sophisticated threats.

Index out of range

Checking the index beforehand is the best way to avoid an inexistent index. In our case, if we wanted to still be able to access the index 2, here’s how we’d do it:

let array = ["1"]

if(array.count >= 3) {
   print(array[2])
} else {
...
}

Force unwrapping

As mentioned at the top, this is a reckless way to build code. There are many ways to avoid force-unwrapping, including guards , *if lets* and default values:

var optionalValue: String? = nil

guard let value = optionalValue else { return }

print(value)

---//---

if let value = optionalValue { 
	print(value) 
}

---//---

print(optionalValue ?? "")

Dividing by zero

One of the approaches we can take is to check whether the divisor is 0. If it is, just return 0.

func divideTenBy(divisor: Int) -> Int {
	
	return divisor > 0 ? (10 / divisor) : 0;
}
...

divideTenBy(0)

Invalid casting of types

We should always check for the type *with is.*

    let a = 10
    if(a is String) {
	    print(a as! String)
    }
    

Use Bugfender to prevent crashes

We’re going to talk about ourselves a bit more now, hope that’s cool. Because we’ve specifically built Bugfender to be a proactive defense shield, not just a crash reporting tool.

By using Bugfender early in your development pipeline you can get an early view of your crashes and solve them, before they start to cause mischief with your end users.

For Bugfender to automatically collect your crash information, you can simply turn it on by using:

Bugfender.enableCrashReporting()

In summary: what to know about iOS crash reports

it is near impossible to have an app without crash occurrences, especially in the early stages of the build. However there are ways to avoid crashes using defensive coding, and also ways to figure out where the issues lie.

What’s more, there are platforms we can use to help us track those issues and have an overview of how often/when they occur to help us mitigate them and fix them as fast as possible.

Hopefully this article has helped you on your way to understanding iOS crashes, and given you the insight you need to mount a proper defense. But you want any more info on how to analyze a crash report and compare the different crash report tools on the market, we’d be happy to help.

Happy coding!