Code Smell 164 - Mixed Indentations

Code Smell 164 - Mixed Indentations

Tabs vs Spaces. The most significant computer problem

Maxi Contieri
·Sep 21, 2022·

2 min read

Subscribe to my newsletter and never miss my upcoming articles

Play this article

Table of contents

  • Problems
  • Solutions
  • Context
  • Sample Code
  • Detection
  • Exceptions
  • Tags
  • Conclusion
  • Relations
  • More Info
  • Disclaimer

TL;DR: Don't mix indentation styles


  • Readability

  • Code consistency

  • Standards violation


  1. Choose one of them

  2. Stick to it

  3. Enforce it with code standards tests

  4. Share the rules on all the codebase

  5. Use an IDE like VS Code or WebStorm that doesn't include tabs at all.


Whenever I publish an article many people don't care about the sample intent and rush to point at indentation mistakes.

Choosing one standard over the other will be a great solution.

Spaces always count as one.

Tabs can count as many different options.

Sample Code


function add(x, y) {
// --->..return x + y;

      return x + y;

function main() {
// --->var x = 5,
// --->....y = 7;

    var x = 5,
        y = 7;


function add(x, y) {
// --->return x + y;
    return x + y;


[X] Automatic

Any parser can enforce this rule.


Some languages like Python consider indent as part of the syntax.

In these languages, indentation is not accidental since it changes code semantics.


  • Code Standards


There's been so much debate on this subject.

The smell is related to mixing them, not about using one instead of another.

Some IDEs automatically convert one convention to the other one.


More Info


Code Smells are just my opinion.

![indentation joke]

Whatever the device you use for getting your information out, it should be the same information.

Tim Berners-Lee

This article is part of the CodeSmell Series.

Share this


Technical Opinions are my own. I don't have the revealed truth.

Software Design is a creative activity. These are hints and not rigid rules.

I write on BackEnd Business Systems and OOP Design. My advice/experience might not suit other systems.

You can write me at info(at)