CSS Modules vs Styled Components: Key Differences and When to Use

Both CSS Modules and Styled Components help style React components with scoped CSS, but CSS Modules use separate CSS files with automatic class name scoping, while Styled Components use JavaScript to create styled React components with dynamic styles. CSS Modules keep styles in CSS files, and Styled Components combine styles and logic in JS.

Quick Comparison

Here is a quick side-by-side look at CSS Modules and Styled Components based on key factors.

Factor	CSS Modules	Styled Components
Styling Method	Separate CSS files with scoped class names	JavaScript tagged template literals for styled React components
Scope	Locally scoped class names by default	Scoped styles tied to components via JS
Dynamic Styling	Limited, requires CSS variables or extra classes	Full dynamic styles using JS props and logic
Setup	Requires CSS loader support in build tools	Requires styled-components library
Performance	CSS is static and cached by browser	Adds runtime JS overhead for style injection
Developer Experience	Familiar CSS syntax, separate files	Co-locates styles with components, JS syntax

Key Differences

CSS Modules work by writing normal CSS in separate files, but the build tool automatically changes class names to unique ones. This means styles only apply to the component that imports them, avoiding conflicts. You still write plain CSS syntax, which is easy to learn and maintain.

Styled Components use JavaScript to create components with styles inside them. You write CSS inside template literals tagged with styled, and you can use JavaScript variables and logic to change styles dynamically based on props or state. This tightly couples styles with component logic.

Because CSS Modules produce static CSS files, they are faster to load and cache well. Styled Components inject styles at runtime, which adds some overhead but allows powerful dynamic styling. The choice depends on whether you prefer separate CSS files or styling inside JS components.

Code Comparison

Here is how you style a simple button with CSS Modules:

css and jsx

/* Button.module.css */
.button {
  background-color: blue;
  color: white;
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}

/* Button.jsx */
import React from 'react';
import styles from './Button.module.css';

export default function Button() {
  return <button className={styles.button}>Click me</button>;
}

Output

A blue button with white text labeled 'Click me' that changes style only inside this component.

Styled Components Equivalent

Here is the same button styled using Styled Components:

jsx

import React from 'react';
import styled from 'styled-components';

const Button = styled.button`
  background-color: blue;
  color: white;
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 4px;
  cursor: pointer;
`;

export default function App() {
  return <Button>Click me</Button>;
}

Output

A blue button with white text labeled 'Click me' styled inside the component using JS.

When to Use Which

Choose CSS Modules when you want to keep styles in separate CSS files, prefer familiar CSS syntax, and want faster static CSS with good caching. It's great for projects where styles and logic are kept apart.

Choose Styled Components when you want to co-locate styles with components, need dynamic styling based on props or state, and prefer writing styles in JavaScript. It's ideal for highly interactive React apps where styles depend on component logic.

Key Takeaways

CSS Modules scope CSS class names automatically using separate CSS files.

Styled Components create styled React components with dynamic styles in JS.

CSS Modules offer better performance with static CSS and caching.

Styled Components allow powerful dynamic styling but add runtime overhead.

Use CSS Modules for simpler static styles and Styled Components for dynamic, JS-driven styles.