Code Smells: What It Is And 5 Easy Ways to Identify

I believe if you are coming from Software Product Development, then you must have come across the term Technical Debt. How often have you actually looked into it and proactively tried to address it? In my early career, when I was just out of college, I didn’t even know any such thing existed. 

They didn’t teach this in my college in those days. Now I am not aware of the course content. It was only after a couple of years that I started working in a product-based organization, and I was introduced to the book “Clean Code” and tools like Sonarqube. I understood the impact of my technical choices.

That’s when I began noticing code smells in everyday code. In this blog, I’ll share what code smells really are, why they signal growing technical debt, and five practical ways I now use to identify them early.

What are Code Smells?

There is an easy approach to avoid technical debt. Look for “code smells”. Code smells meaning can simply be termed as the symptoms within the codebase that can indicate - there might be larger issues hidden in the codebase. Code smells are not necessarily bugs/defects that will prevent a feature or application from working, but more of an indicator of a flaw existing in the overall design, architecture, or code.

If you’re wondering what happens after identifying code smells, this article on measuring and controlling technical debt explores practical ways teams can track and manage it over time.

What is Technical Debt?

Technical debt refers to every technical choice that one makes while trading off quality for speed. It is an implicit cost of future rework when choosing an easy, fast solution over a better, more robust approach. Technical debt can be incurred consciously or unconsciously. Consciously is when the Developers choose a shortcut over the correct approach to gain speed. Unconsciously is when the Developers don’t know any better and only realize that it is technical debt in hindsight. 

Understanding and knowing the technical debt is important. Like financial debt, it accrues interest. That interest will have to be paid in the form of slower development, hidden bugs, and an unmanageable, unreliable, unstable codebase.

Want to go deeper? Here’s a post about how technical debt and undone work quietly accumulate and why teams often underestimate their long-term impact.

Types of code smell

Over the years, I’ve learned that while there are many code smells documented, a small set keeps showing up again and again in real-world codebases. Broadly, these smells fall into two categories: within classes and between classes. Understanding this split makes common code smells examples easier to spot and fix. Here is a list of code smells: 

Code Smells Within Classes

Smells found in a class or method typically indicate increasing (complexity) or decreasing (readability).

• Excessive Comments: If code needs excessive explanation, it's a good bet that its intent is not clear. The class and method names should provide most of the explanation for this. Logical constructs that are hard to explain are generally better refactored than written as comments.

• Long Methods: Methods that seem to go on forever can be difficult to read, test, and reuse. If you break up the complex logic into smaller and more focused methods, you improve the readability of your code without changing the behavior.

• Long Parameter Lists: Methods that require many parameters to use and reason about are more challenging and confusing. In many cases, parameter values that belong together can be grouped, or derived, from tests that execute internally, leading to cleaner and easier-to-read code.

• Large Classes: Classes grow over time without warning, and when a single class attempts to perform a number of unrelated tasks, it's extremely difficult to support that code. Splitting a single class's responsibility for task definitions into multiple classes restores focus and keeps things simple.

• Duplicate Code: Code that appears multiple times in multiple methods would be considered duplicate and would require additional effort to maintain. Coding all instances of shared behavior in a single place reduces opportunities for introducing bugs when changes are made.

• Dead Code: Code that has never been called adds clutter and confusion to the codebase. When these pieces of code are removed, the codebase becomes cleaner and helps to reduce the ongoing cost of maintaining the remaining code.

Code Smells Between Classes

Classes that do not interact or fail to interact with other classes cause various code smells.

• Data Classes: Classes that contain only data and no behavior are an indication that you are not using an object-oriented design. Cohesion can be improved by grouping related behaviour with the corresponding data.

• Data Clumps: When you repeatedly see the same group of variables together, it is a good indication that the variables belong as a new class.

Alternative Classes with Different Interfaces

Classes having the same general functionality but elucidating different method names can create an increase in cognitive load. Having these classes aligned by a common interface will result in a more consistent implementation.

• The Refused Bequest: Typically when the inheritance chain is not completely utilized, it will point to a faulty hierarchy; thus, a Composite Pattern communicates intent better than the Inheritance Pattern.

• The Lazy Class: A Class that provides little value during refactoring will cause a decrease in team productivity. Therefore, either removing these classes or merging them into other Classes can be a boon to your design and help to maintain a lean design.

• Shotgun Surgery: When a minor change requires a number of Classes to be modified, the Classes are not properly encapsulated and the responsibilities of one Class may have been scattered. Bringing related classes together in one area will result in a system that will evolve more easily.

5 Easy Ways to Identify Code Smells

Over time, I realized that most code smells are not hidden or complex; they show up repeatedly in day-to-day development. Once you learn what to look for, identifying them becomes easier and far more intentional. Here are my top 5 ways to identify code smells: 

1. Dead Code

This is the easiest to identify code smell. Dead code is the piece of code that is never executed. When ‘If’ statements are written that check a condition which will never occur, or a ‘switch’ defining a case that is not possible, or when writing a ‘try-catch’ block where the code cannot end up in the ‘catch’ block, are all examples of “Dead Code”.

The Fix: Write Unit Tests and execute them often. Check which part of the code is being executed and which is never touched. If not a single unit test case can get to a piece of code, then it is an indication that the piece of code eventually would become Dead code.

2. Hardcoded Values

Another common practice that degrades the maintainability of code is hardcoding values. For ex: $calcMail = new rCaptchaMail(xEn@bl30891Ma!l3r); or If (env == “QA”). If in the future such elements need to be updated with a different value, it would be hard to locate and fix. If it is in one place, maybe it is doable, but if it is duplicated across the codebase, the task becomes even more difficult.

The Fix: Don’t hardcode. There is no other way. Even if one thinks they can recall where the hardcode was created, when the time comes, no one knows.

3. Code Duplication

Code Duplication is another easy way to accumulate Technical Debt. Copy pasting similar lines of code not only bloats up the codebase, but it also increases the amount of effort required to make any changes if needed in the future. Also, it creates an opportunity for an error to go unnoticed.

The Fix: A simple engineering principle, DRY - do not repeat yourself. One of the learnings I have had while writing code to avoid duplication is - if the code needs to be duplicated for a third time, it means that it needs a function of its own. 

4. One-Stop Shop Class

Have you ever come across a Class file that typically does everything for the application? For ex, you may have a User Class that will not only create and manage the User profile, but also often validates the user, or may authenticate the user, and may be more. 

Well, such a class is another great example of Technical Debt. One class doing multiple things leads to multiple points of failure and makes the codebase brittle. Developers often fear touching such code files because they don’t know what else might break if they try to correct some piece of code.

The Fix: SRP - Single Responsibility Principle or ISP - Interface Segregation Principle. And this doesn’t just apply to classes or interfaces, but every method, every function should have only one entry and one exit point. This gives complete control and understanding of what is working and what has failed. 

Not all technical debt is created equal. This related post breaks down whether all technical debt is actually bad and when it might be a conscious trade-off.

5. Too Much to Handle - The Big Code File

In my personal experience, having about 150-200 lines of code is maintainable. As the number of lines of code increases within a single file, and to top it off, this code is full of if…else statements and multiple loops, it suddenly becomes a maintenance nightmare. This creates a high cyclomatic complexity in the file, indicating that the code is again trying to do too many things.

The Fix: Refactor and refactor again. Break long methods into smaller, private methods with descriptive names. Too many ‘ifs’, see if every condition can become a function on its own.

Many teams ask if a “zero technical debt” codebase is even realistic. Explore this question in detail in Can teams avoid technical debt completely?

Simple Practices To Prevent Code Smells

Preventing code smells is far easier than fixing them later. These are a few simple practices I consciously follow to keep my codebase clean, readable, and maintainable.

• Stick to SOLID principles: I try to apply all five SOLID principles wherever possible. They naturally encourage modular design, clear responsibilities, and loosely coupled code, which significantly reduces the chances of code smells creeping in.

• Use self-documenting names: Clear and intention-revealing names for classes, methods, and variables often eliminate the need for comments. When the code explains itself, understanding and maintaining it becomes much easier.

• Keep methods small and focused: Every method should do one thing and do it well. Short, focused methods are easier to test, reuse, and modify without introducing unintended side effects.

• Refactor continuously: I don’t wait for a “big refactoring phase.” Small improvements made regularly prevent minor issues from turning into long-term technical debt.

• Prefer composition over inheritance: Instead of building deep inheritance hierarchies, I favor combining small, reusable components. This approach gives more flexibility and keeps the design simpler and easier to evolve.
  
  

These habits don’t eliminate code smells entirely, but they drastically reduce how often they appear and how costly they become over time.