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Code & Deliverynoun · /koʊd smɛl/

code smell

In simple English

Code smell is a term coined by Kent Beck and popularized by Martin Fowler to describe patterns or characteristics in code that look suspicious but are not definitive errors. Examples include duplicate code, overly long functions, classes with too many responsibilities, or cryptic variable names. These signals suggest the code may be harder to maintain, test, or understand than it should be. In real tech workplaces, developers use code smell during code reviews to flag sections worth refactoring. It is a neutral, non-accusatory way to suggest improvements without claiming the code is broken. When someone says, 'I smell a code smell here,' they are inviting discussion about whether the code structure could be improved for better maintainability, readability, or performance. Code smell is central to clean code practices and agile development methodologies. Teams often establish standards for what counts as a code smell in their specific project, and static analysis tools can automatically detect many common smells like unused variables, extremely long methods, or high cyclomatic complexity.

What patterns and characteristics in code indicate potential quality or design problems?

At a glanceCEFR C1
Commonness4/5
Versatility4/5
FormalityCasualFormalNeutral
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticDirect
RegionUS and UK
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Say it like this

✓I smell a code smell in this function.
✓That method has some obvious code smells we should refactor.
✓Let us address these code smells before the next release.

Real examples

in a standup

"We identified some code smells in the authentication module during yesterday's review, so we allocated time to refactor this sprint."

in a code review

"This function is 200 lines long and handles five different responsibilities—that is a code smell indicating we should split it into smaller methods."

in a team meeting

"Before we ship this feature, let us do a quick pass to catch any code smells and clean up technical debt."

Don't say this

Handle with care. Code smell is not a literal smell and does not indicate a bug exists. It signals potential quality issues that need investigation, not confirmed problems.

✕We found a code smell, so we must revert the entire feature.
✓We found code smells that suggest the code could be refactored for better readability.— Code smell indicates potential issues requiring investigation, not confirmed bugs that must be reverted immediately.
✕The code does not have a smell, so it is perfect.
✓The code does not have obvious code smells, though it may still have logical issues or bugs.— Absence of code smell does not guarantee correctness; it only means the structure looks clean.
✕Code smell is a type of bug.
✓Code smell is a sign that code might benefit from refactoring or review.— A code smell is a warning sign, not a confirmed defect or error.

Other forms

noun

code smell

"This code smell suggests the function is doing too much."

noun (plural)

code smells

"We found several code smells during the refactoring audit."

verb phrase

smell a code smell

"I smell a code smell—let us review this logic together."

Often used with

detect code smellsTo identify or find code smells, often using tools or code review.
address code smellsTo fix, refactor, or improve code flagged as having code smells.
obvious code smellA clear or easily recognizable code smell that stands out.
refactor code smellsTo rewrite or restructure code to eliminate code smells.
code smell analysisThe process of identifying and evaluating code smells in a codebase.

Similar words

red flagA general warning sign; code smell is more specific to code structure and design.
anti-patternA repeated solution that is ineffective; similar but broader than code smell.
technical debt indicatorSuggests maintenance burden; code smell is more about code structure specifically.

Opposites

clean codebest practicewell-structured code

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Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. You notice a function with 15 parameters. What do you say in a code review?

Complete the sentence

2. The linter found several _______ in the payment module that we should address before release.

Spot the mistake

3. Which sentence uses code smell incorrectly?

Rewrite naturally

4. Rewrite this in natural tech English using code smell: 'This part of the code looks suspicious because it has a really long function that does many different things, and we should probably make it better.'

Questions

Quick poll

Have you said "code smell" in a standup this week?

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