Different Ways To Write CSS In React: Complete 2025 Guide

React's component-based architecture offers incredible flexibility in how you approach styling. Unlike traditional web development where CSS lives in separate files, React allows you to integrate styling directly into your component workflow--each approach with distinct advantages for different project needs.

The evolution of CSS in the React ecosystem has been driven by the need for better component isolation, improved developer experience, and optimized performance. From the early days of global CSS files and BEM naming conventions to modern utility-first frameworks, developers now have more options than ever before.

At Digital Thrive, we leverage modern web development practices using Next.js combined with Tailwind CSS as our primary styling stack. This combination delivers exceptional performance through build-time optimization while maintaining the flexibility needed for complex design systems. However, understanding all available options helps you make informed decisions based on your specific project requirements.

Traditional CSS/SCSS: The Foundation

The classic approach to styling React applications involves importing CSS files directly into your components. This method has stood the test of time and remains viable for many projects, particularly those with simpler styling requirements or teams already familiar with traditional CSS workflows.

CSS preprocessing with SCSS or Less adds powerful features like variables, nested rules, and mixins that make stylesheets more maintainable. When combined with CSS methodologies like BEM (Block Element Modifier), teams can create organized stylesheets that scale reasonably well.

The primary challenge with traditional CSS in React is global scope pollution. Without careful organization, class names can conflict across components, leading to unexpected styling issues that can be difficult to debug.

// Component.jsx
import './Button.css';

function Button({ variant, children }) {
 return (
 <button className={`btn btn--${variant}`}>
 {children}
 </button>
 );
}

// Button.css
.btn {
 padding: 0.75rem 1.5rem;
 border: none;
 border-radius: 6px;
 font-weight: 600;
 cursor: pointer;
 transition: all 0.2s ease;
}

.btn--primary {
 background-color: #2563eb;
 color: white;
}

.btn--secondary {
 background-color: #64748b;
 color: white;
}

.btn--outline {
 background-color: transparent;
 border: 2px solid #2563eb;
 color: #2563eb;
}

Traditional CSS works well when you need straightforward styling without additional dependencies, have existing CSS codebase to maintain, or prefer simplicity over advanced features. Many teams find that combining traditional CSS with a naming methodology provides adequate isolation for small to medium-sized applications.

For teams working with modern CSS features, understanding concepts like the CSS nth-of-class selector can help solve complex styling challenges without adding extra markup.

CSS Modules: Local Scope Solution

CSS Modules address the global scope problem by automatically generating unique class names for your styles. This build-time transformation ensures that your component styles never conflict with styles elsewhere in your application, providing true component isolation without manual naming conventions.

The approach is straightforward: write your CSS as you normally would, then import it into your component as a JavaScript object. The build tool handles the transformation, ensuring each class name is uniquely scoped to its component. This makes CSS Modules particularly valuable for larger applications where multiple teams work on different components simultaneously.

As noted in the CSS Modules documentation, this approach provides local scoping by default while maintaining all the familiar CSS syntax you're already comfortable with. The generated class names are deterministic, meaning they'll be consistent across builds, which helps with caching and server-side rendering.

// Button.module.css
.button {
 padding: 0.75rem 1.5rem;
 border: none;
 border-radius: 6px;
 font-weight: 600;
 cursor: pointer;
 transition: all 0.2s ease;
}

.primary {
 background-color: #2563eb;
 color: white;
}

.primary:hover {
 background-color: #1d4ed8;
 transform: translateY(-1px);
}

.secondary {
 background-color: #64748b;
 color: white;
}

.secondary:hover {
 background-color: #475569;
}

.outline {
 background-color: transparent;
 border: 2px solid #2563eb;
 color: #2563eb;
}

// Button.jsx
import styles from './Button.module.css';

function Button({ variant = 'primary', children }) {
 return (
 <button className={`${styles.button} ${styles[variant]}`}>
 {children}
 </button>
 );
}

CSS Modules excel in component libraries and design systems where isolation is critical. They also integrate seamlessly with Next.js and other modern React frameworks, requiring no additional configuration in most cases.

Advanced CSS Modules techniques, such as those used when animating CSS Grid layouts, demonstrate how this approach maintains the full power of CSS while providing component isolation.

CSS-in-JS: Dynamic Styling Solutions

CSS-in-JS libraries bring styling directly into your JavaScript components using tagged template literals. This approach offers powerful capabilities for dynamic styling based on props, state, and theme context--capabilities that are difficult or impossible to achieve with traditional CSS approaches.

The runtime nature of CSS-in-JS means styles can respond to any JavaScript value in your component. This enables sophisticated interactive behaviors like hover states based on complex conditions, theme switching without page reloads, and responsive styles tied to component props. The Styled Components documentation demonstrates how tagged template literals create a natural syntax for defining component-scoped styles.

Two prominent libraries dominate this space: styled-components and Emotion. Both offer similar capabilities with subtle differences in API design and performance characteristics.

Styled Components

Styled-components popularized the tagged template literal approach, allowing you to create components directly from your styles. The syntax reads naturally, with CSS rules embedded directly in your JavaScript. Theme providers enable application-wide design tokens that components can access without prop drilling.

import styled, { ThemeProvider, css } from 'styled-components';

const Button = styled.button`
 padding: 0.75rem 1.5rem;
 border: none;
 border-radius: 6px;
 font-weight: 600;
 cursor: pointer;
 transition: all 0.2s ease;
 background-color: ${props => props.$primary 
 ? props.theme.colors.primary 
 : props.theme.colors.secondary
 };
 color: white;

 ${props => props.$outline && css`
 background-color: transparent;
 border: 2px solid ${props.theme.colors.primary};
 color: ${props.theme.colors.primary};
 `}

 &:hover {
 transform: translateY(-1px);
 box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
 }
`;

// Usage with theme
function App() {
 return (
 <ThemeProvider theme={{ 
 colors: { primary: '#2563eb', secondary: '#64748b' } 
 }}>
 <Button $primary>Primary Action</Button>
 <Button $outline>Outline Button</Button>
 </ThemeProvider>
 );
}

Emotion

Emotion offers similar functionality with two distinct APIs: the css prop for inline-like styling and the styled API for creating styled components. The Emotion documentation highlights its performance-focused design with optional zero-runtime configurations for production optimization.

/** @jsxImportSource @emotion/react */
import { css } from '@emotion/react';

const buttonBase = css`
 padding: 0.75rem 1.5rem;
 border: none;
 border-radius: 6px;
 font-weight: 600;
 cursor: pointer;
 transition: all 0.2s ease;
 background-color: ${props => props.$variant === 'primary' 
 ? '#2563eb' 
 : '#64748b'
 };
 color: white;

 &:hover {
 transform: translateY(-1px);
 }
`;

function Button({ variant = 'primary', children, ...props }) {
 return (
 <button css={buttonBase} data-variant={variant} {...props}>
 {children}
 </button>
 );
}

CSS-in-JS solutions shine in applications requiring dynamic theming, interactive component behaviors, or component libraries that need to accept complex style props. The tradeoff is a small runtime overhead and larger bundle sizes compared to build-time solutions.

Utility-First CSS: Tailwind CSS

The utility-first approach revolutionized how developers think about CSS. Rather than writing custom CSS for each component, you compose designs using small, single-purpose utility classes. This methodology, championed by Tailwind CSS, dramatically speeds up development while ensuring consistency through a predefined design system.

Tailwind's utility classes handle every CSS property you might need: spacing, sizing, colors, typography, flexbox, grid, and more. The key advantage is never having to switch between HTML and CSS files--you write your styles directly in your markup. The JIT (Just-In-Time) compiler generates only the CSS you actually use, keeping production bundles remarkably small.

function Button({ variant = 'primary', children, className = '', ...props }) {
 const baseClasses = 'px-6 py-3 font-semibold rounded-lg transition-all duration-200 ease-in-out';
 
 const variantClasses = {
 primary: 'bg-blue-600 text-white hover:bg-blue-700 focus:ring-2 focus:ring-blue-500 focus:ring-offset-2',
 secondary: 'bg-gray-600 text-white hover:bg-gray-700 focus:ring-2 focus:ring-gray-500 focus:ring-offset-2',
 outline: 'border-2 border-blue-600 text-blue-600 hover:bg-blue-50 focus:ring-2 focus:ring-blue-500 focus:ring-offset-2'
 };

 return (
 <button
 className={`${baseClasses} ${variantClasses[variant]} ${className}`}
 {...props}
 >
 {children}
 </button>
 );
}

// Responsive card with hover effects
function Card({ title, description, imageUrl }) {
 return (
 <div className="max-w-md mx-auto bg-white rounded-xl shadow-md overflow-hidden hover:shadow-xl transition-shadow duration-300">
 <div className="md:flex">
 <div className="md:shrink-0">
 <img 
 className="h-48 w-full object-cover md:h-full md:w-48" 
 src={imageUrl} 
 alt={title} 
 />
 </div>
 <div className="p-6">
 <span className="text-sm text-blue-600 font-semibold uppercase tracking-wide">
 Article
 </span>
 <h3 className="block mt-1 text-lg font-medium text-gray-900">
 {title}
 </h3>
 <p className="mt-2 text-gray-600 leading-relaxed">
 {description}
 </p>
 </div>
 </div>
 </div>
 );
}

Tailwind's responsive prefixes (sm:, md:, lg:, xl:, 2xl:) make adapting layouts for different screen sizes straightforward. State variants like hover:, focus:, and active: handle interactive states without custom CSS. The framework also supports dark mode, custom configurations, and a powerful plugin system for extending functionality.

For organizations building design systems, Tailwind enables you to extract repeated patterns into reusable components while maintaining the flexibility to customize as needed. The framework's configuration file defines your design tokens, ensuring every button, input, and card follows your established visual language.

To achieve optimal performance with utility-first CSS, understanding critical CSS optimization techniques ensures your React applications load quickly and deliver excellent user experiences.

Integration with Next.js and Modern React

Modern React frameworks like Next.js provide excellent support for all CSS approaches. The App Router in Next.js 14+ handles CSS imports automatically, while CSS Modules and Tailwind CSS require minimal configuration to get started.

For Server Components, CSS remains the preferred styling method since runtime solutions like CSS-in-JS require client-side JavaScript execution. This architectural consideration makes build-time solutions increasingly attractive for new projects targeting optimal performance.

At Digital Thrive, our web development services leverage Next.js with Tailwind CSS to deliver exceptional performance and maintainability. This combination provides the benefits of utility-first development with Next.js's built-in optimizations for production deployments. Our approach ensures fast page loads, excellent Core Web Vitals scores, and maintainable codebases that scale with your business needs.

When building modern React applications, consider your performance requirements from the start. The choice between build-time and runtime styling has implications for bundle size, initial page load, and user experience across devices and network conditions. For teams working with styled code in and out of blocks, consistent styling patterns across your codebase reduce cognitive load and maintenance overhead.

Sources

1. Styled Components Documentation - Official documentation for the popular CSS-in-JS library
2. Tailwind CSS Utility-First Documentation - Guide to utility-first CSS methodology
3. CSS Modules GitHub Repository - Documentation for local scope CSS solutions
4. Emotion CSS-in-JS Documentation - Performance-focused CSS-in-JS library documentation