Why SCSS is Still Better Than CSS-in-JS for React Applications

Photo by Niels Kehl on Unsplash

In the ever-evolving world of front-end development, styling solutions have been a hot topic for years. While CSS-in-JS solutions like Styled Components and Emotion have gained popularity in React applications, SCSS (Sass) remains a powerful and efficient way to style applications.

If you’re wondering which approach to choose for your next project, let’s dive deep into the pros and cons of SCSS vs. CSS-in-JS and why SCSS might still be the better choice in 2025! 🔥

1. What is SCSS? 💡

SCSS is a preprocessor for CSS that extends its capabilities by adding features like variables, nesting, mixins, and functions. It makes writing styles more maintainable and scalable.

Example of SCSS:

$primary-color: #007bff;

.button {
  background-color: $primary-color;
  padding: 10px 20px;
  border-radius: 5px;
  color: white;
  font-weight: bold;
  transition: background 0.3s;

  &:hover {
    background-color: darken($primary-color, 10%);
  }
}

This simple SCSS example defines a button style with a primary color variable, nesting, and a hover effect.

2. What is CSS-in-JS? 🎨

CSS-in-JS is a styling approach where CSS is written inside JavaScript. Some popular libraries include Styled Components and Emotion.

Example of Styled Components:

import styled from 'styled-components';

const Button = styled.button`
  background-color: #007bff;
  padding: 10px 20px;
  border-radius: 5px;
  color: white;
  font-weight: bold;
  transition: background 0.3s;

  &:hover {
    background-color: darken(#007bff, 10%);
  }
`;

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

While it looks similar to SCSS, there are fundamental differences under the hood. Let’s analyze both approaches in depth.

3. Pros of SCSS ✅

🔥 Better Performance

SCSS is precompiled, meaning styles are generated at build time, leading to better runtime performance. CSS-in-JS generates styles dynamically, which can impact page load times and re-rendering performance.

🎯 Separation of Concerns

SCSS keeps styles separate from JavaScript logic, promoting cleaner and more maintainable code. With CSS-in-JS, styles are tightly coupled with components, which can lead to bloated files.

🚀 Faster Development with Mixins & Functions

SCSS offers powerful mixins and functions that eliminate redundant code. Example:

@mixin button-style($color) {
  background-color: $color;
  padding: 10px 20px;
  border-radius: 5px;
  color: white;
  font-weight: bold;
}

.button-primary {
  @include button-style(#007bff);
}

.button-secondary {
  @include button-style(#6c757d);
}

4. Cons of SCSS ❌

🛑 Requires a Build Step

Since SCSS needs to be compiled to CSS, a build tool like Webpack or Vite is required.

⏳ No Dynamic Styles

SCSS cannot generate styles dynamically at runtime like CSS-in-JS can. If you need styles that change based on props, you’ll have to use CSS variables or additional class toggling.

5. Pros of CSS-in-JS ✅

🎨 Scoped Styles by Default

CSS-in-JS avoids style conflicts by scoping styles automatically to components.

🧑‍💻 Dynamic Styling with Props

Styled Components allows you to pass props and generate styles dynamically:

const Button = styled.button`
  background-color: ${props => props.primary ? '#007bff' : '#6c757d'};
`;

📦 No Additional Build Step Needed

Since styles are generated at runtime, no preprocessor is required.

6. Cons of CSS-in-JS ❌

🐢 Performance Overhead

Generating styles at runtime can slow down rendering, especially in large applications.

🔄 Larger Bundle Size

CSS-in-JS solutions increase JavaScript bundle size since styles are included in JS files.

🤯 Harder to Debug

Since styles are dynamically generated, debugging and overriding styles in DevTools can be more complex compared to traditional CSS/SCSS.

7. Conclusion 🎯

Both SCSS and CSS-in-JS have their use cases, but SCSS remains a strong choice for many React applications due to its better performance, maintainability, and ease of debugging. If you want scoped styles with dynamic capabilities, CSS-in-JS can be helpful, but the trade-offs in performance and bundle size must be considered.

👉 Best of Both Worlds? You can even use SCSS for global and reusable styles while leveraging CSS-in-JS selectively for truly dynamic styling needs.

What’s your preferred styling approach? Let’s discuss in the comments! 💬