What Are the Types of Software Bugs?

That’s why ongoing testing and debugging are so important. By putting the appropriate processes in place today, you can improve the reliability and security of your systems while safeguarding the user experience.

Take the first step in that process with this overview of the most common types of software bugs, examples of how they show up in practice, and the impact they can have on your team and business. We’ll also cover prevention strategies to avoid unwanted outcomes like app crashes and downtime.

Suggested reading, “The Development Scale Paradox: Why Bigger Isn't Better for Innovation.”

What Are the Types of Software Bugs? Examples and Explanations

The first step is to understand the types of bugs you may encounter when rolling out new products and making updates. Here’s a look at some of the most common issues that arise in software, along with examples and explanations for addressing them.

Functional Bugs

A functional bug occurs when software doesn’t perform according to its expectations. For example, a user may click "save" on a document that fails to save on their device. Or they might try to use the search bar but not see any results. These issues tend to relate back to misinterpreted specifications in the coding, incomplete logic, and human error.

How To Fix: To resolve a functional bug, developers typically review documentation requirements, reproduce the issue, and use targeted regression testing. You can avoid these bugs moving forward by focusing on creating clear documentation so that developers understand exactly what the software is supposed to do. Leverage user acceptance testing (UAT) to test code in real-world scenarios before release.

Logical Bugs

Logical bugs feature code that executes successfully but produces incorrect outcomes, typically due to flawed logic or misplaced conditions. They often come from faulty algorithms and misunderstandings of how different code works together in a system.

You can find these bugs by looking for instances where calculations or outputs appear inconsistent with your business rules. For example, an e-commerce app might apply the same discount twice, which is not a deal the brand intended to offer.

How To Fix: Developers can fix these bugs by reviewing logic flow, testing edge cases, and using pair programming to detect faulty reasoning before it makes it into deployment.

Workflow Bugs

Workflow bugs happen when there’s an unintended sequence of actions or operations. For example, a user might complete the checkout process only to be sent back to the payment screen.

How To Fix: To resolve these, developers need to trace the full path of user interactions and correct any missing transition logic. You can proactively prevent such bugs through usability testing, flow diagrams, and other forms of automated testing. These can help you catch workflow issues before they impact the end user.

Unit-Level Bugs

Unit-level bugs exist within isolated parts of your codebase, such as a single function or class. They’re often caused by unhandled exceptions and incorrect assumptions. You’ll recognize them when a specific module crashes in isolation or a unit test you run fails. For instance, if you have a function that divides numbers, it could give you a unit error if you try dividing by zero.

How To Fix: The solution to these bugs is typically focusing on writing stronger test cases. You might also need to mock dependencies better before deployment and apply more boundary checks.

System-Level Integration Bugs

System-level bugs happen when separate modules or services interact incorrectly. For example, your checkout page might confirm a purchase without updating the inventory database. These are often caused by incompatible data formats or mismatched API responses.

How To Fix: To solve system-level bugs, teams can synchronize their environments and conduct more in-depth contract testing. You may also be able to find them through continuous integration pipelines that detect problems automatically as you release new deployments.

Out-of-Bound Bugs

Bugs are “out-of-bounds” when their program tries to access data outside a valid range. For example, if you have an array of 20 numbers and a program tries to call the 22nd number, that could deliver an out-of-bounds bug. These are often caused by incorrect loop conditions and missed input checks.

How To Fix: You can fix these problems by adding stricter boundary validations to your workflow. Tools like AddressSanitizer and Valgrind can help you detect these bugs during testing.

Security Bugs

Security bugs relate to issues of unauthorized access, leaked data, and malicious exploitation. They’re typically caused by unsafe coding practices and poor authentication mechanisms. You can find them through penetration testing or by reviewing your system logs for suspicious activity. For example, a bad actor may use an SQL injection attack to manipulate your database.

How To Fix: A developer would address that bug by applying stricter encryption, sanitizing the inputs, and enforcing the principle of least-privilege access. This essentially means giving employees access to only those systems and databases they need to do their work. Regular security checks and dependency patching are also important here.

Performance Bugs

Performance bugs impact the speed or efficiency of your systems without breaking their core functionality. For example, a dashboard might take 15 seconds to load instead of updating with new data instantly. This could create performance bottlenecks that multiply across your workforce.

How To Fix: To fix performance bugs, developers generally work on re-optimizing the code. Add caching and load-balancing components to avoid bottlenecks that can slow progress. Continuous monitoring is also important, as it helps catch performance bugs that arise as different systems evolve independently.

Compatibility Bugs

Compatibility bugs exist when software behaves differently across different devices and operating systems. They’re often caused by outdated APIs or unsupported libraries. For example, your web app may work on Chrome but break on Safari browsers.

How To Fix: To solve this problem, focus on cross-platform testing. You may also need to maintain environment-specific configurations. For example, your codebase may need to deliver something different based on whether the user is accessing your app on Mozilla Firefox or another browser.

Usability Bugs

Usability bugs make software harder to use or less intuitive for your audience. They tend to come from poor interface design and confusing labels, among other problems. For example, a “submit” button placed below your page fold may lead to users missing the form entirely and harm your lead generation.

How To Fix: Fixing these types of bugs is typically about refining the front-end user interface. You can do that through accessibility testing, direct updates, or feedback sessions with real users. You’ll also want to complete regular reviews to ensure your critical software continuously performs at the level your end users expect.

Concurrency Bugs

Finally, concurrency bugs happen when multiple processes access shared resources at the same time. This can lead to unpredictable outcomes that make your software inefficient or outright wrong. For example, two users might edit a document at the same time and overwrite one another’s changes without realizing it.

How To Fix: Developers can solve concurrency bugs by stress-testing systems under concurrent workloads. You may also want to add better synchronization mechanisms to your software as a preventative step.

The Impact of Software Bugs

Software bugs can cause an array of problems for your company. For instance, one review found that software defects cost U.S. companies more than $2.4 trillion annually. A single bug can impact revenue and usage directly. Other challenges you may face include:

• Delayed releases: When your IT team has to spend hours debugging new releases, it can slow delivery and put your company’s reputation at risk. Missing release dates or rolling out bugged products may put you behind the curve at a time when you should be focusing on ongoing user-centric optimization.
• Increased costs: Bugs increase the number of QA cycles you go through and the amount of rework you have to complete as part of your development process. This increases the amount of labor you spend per release, which adds to your overall costs.
• Reputational damage: Users can lose trust in your brand after major crashes and data losses caused by bugs. This can cause lasting damage that makes it difficult to achieve your growth goals. You may end up having to spend even more money repairing the reputational harm.
• Security risks: Bugs often trace back to security vulnerabilities. If you aren’t aware of them or take your time fixing them, these could be exploited. For example, a hacker may steal your sensitive data or cause a major outage that takes days to repair.

In the end, buggy code may lead to many different risks that can harm your company’s reputation in the industry and sour customer trust. That means your policies for preventing bugs and debugging software can have a direct impact on your bottom line.

Best Practices for Preventing and Debugging Software Bugs

Given the importance of debugging, it’s worth reviewing best practices to make sure your company is on the right track.

The best way to solve the problem of software bugs is to prevent them before they ever happen. That starts by crafting clean, modular, and well-documented code. Each component in your designs should serve a clear purpose and be easy for others to understand. Code that’s simple to read today will be much easier to debug months or years down the road.

Consistency matters, too. Try to use standard naming conventions and style guides across your entire codebase and team. This reduces confusion and prevents the kind of subtle errors that can slip through initial testing but cause persistent bugs down the line.

Automation also has a role to play, especially with the advent of AI coding tools. These can help you catch syntax errors and potential security flaws earlier in your development process. You can use static code analysis and linting tools initially and pair them with automated testing frameworks. That way, you’re verifying that both individual functions and the system as a whole behave as expected before deployment.

Modern error detection tools accelerate identification and resolution timelines. However, they aren't a replacement for human oversight. For example, a 2024 empirical comparison of analysis tools found significant variability in performance. With automated tools still missing a meaningful number of software defects, it's important to complete peer reviews and collaborative code walk-throughs to catch overlooked edge cases and logic errors.

Finally, practice defensive programming. This means anticipating potential errors as you work, instead of only catching them after the fact. It’s a good mindset to get into, as it can cut down on the amount of debugging you have to do later and potentially save hours of labor for your company.

How To Debug Software Bugs

Even the most careful developers still run into bugs. When they come up, the goal is to find their cause and fix them quickly without introducing any new issues in the process. But that’s often easier said than done. It's also a critical problem to solve, as a single interruption in a worker's day, such as having to deal with a sudden bug, can take over 25 minutes to recover from.

To debug code, begin by reproducing and isolating the problem that you’ve found in a controlled environment. Recreate the conditions where the bug occurred and trigger it again to find its root cause while ruling out unrelated factors.

Another key step is tracing a problem back to the exact point of failure. Structured logging, breakpoints, and debugging tools can isolate where and why the code broke down, making it easier to reproduce and resolve issues quickly.

Then review your recent deployments, dependency updates, and configuration changes. Many bugs come from recent additions to your code base. These are often the easiest to solve, so it’s worth ruling them out first.

If you have a particularly hard time solving a bug, consider collaborating with a teammate for pair debugging sessions. Each party gains a fresh perspective on the problem and helps reduce blind spots.

Once you’ve found the problem, you can verify it through regression testing. This will make sure that the bug didn’t create any new problems elsewhere in your systems. You’ll want to wrap the process up by documenting each issue resolved in a bug tracker or internal wiki. That way, it’s much easier to solve in the future if it happens again.

The Bottom Line on Software Bugs

In software development, bugs are inevitable, but their impact doesn't have to be. Your method of response is what will separate a resilient system from a fragile one. Use these debugging tips to find, fix, and move on from software hiccups faster, keeping the most common types of bugs and their solutions top of mind.

Remember, the best developers do more than react when problems arise. They proactively build testing frameworks, leverage automation, and create workflows that catch issues before they reach production. By investing in prevention today, you can protect not only your code but your users' trust and your company's bottom line.

About the Author

Hannah Hicklen Content Marketing Manager at Clutch

Hannah Hicklen is a content marketing manager who focuses on creating newsworthy content around tech services, such as software and web development, AI, and cybersecurity. With a background in SEO and editorial content, she now specializes in creating multi-channel marketing strategies that drive engagement, build brand authority, and generate high-quality leads. Hannah leverages data-driven insights and industry trends to craft compelling narratives that resonate with technical and non-technical audiences alike. 

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