Things You Can Do With CSS Today

CSS has evolved far beyond its origins as a simple styling language. Modern CSS now handles responsibilities that once required JavaScript--interactive UI states, scroll-linked animations, responsive component behavior, and even page transitions. This guide explores the powerful features you can use today to build faster, more maintainable web interfaces without sacrificing user experience or browser compatibility.

Why Modern CSS Matters for Performance

Modern CSS features offer significant performance advantages over JavaScript-based alternatives. CSS runs on the browser's rendering engine, optimized over decades for efficient style calculations and layout operations. When you replace JavaScript event listeners and DOM manipulations with native CSS equivalents, you eliminate main thread work, reduce bundle size, and leverage hardware-accelerated animations, as documented in DEV Community's comprehensive CSS guide.

By building with modern CSS, your web development projects benefit from better Core Web Vitals scores, improved accessibility through native semantic elements, and easier maintenance through well-organized stylesheets. For teams looking to maximize performance, combining modern CSS techniques with professional web development services ensures your interfaces are both beautiful and blazing fast across all devices.

Interactive UIs with the :has() Pseudo-Class

The :has() pseudo-class represents a powerful shift in what's possible with CSS selectors. Previously, CSS could only select elements based on their descendants or siblings that followed them. With :has(), you can select elements based on their children--a pattern previously impossible without JavaScript.

Parent Selection Without JavaScript

The most impactful use of :has() is parent selection. Consider a form validation scenario where you want to style a form group differently when its input is invalid:

.form-group:has(input:invalid) {
 border-color: #ef4444;
 background-color: #fef2f2;
}

.form-group:has(input:focus) {
 border-color: #3b82f6;
 box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

This pattern eliminates the need for JavaScript event listeners that toggle classes based on validation state. The browser handles all calculations natively, and the styling updates happen instantaneously as users interact with the form, as demonstrated by OpenReplay's modern CSS features guide.

For teams working with React applications, :has() can significantly reduce the amount of client-side state management needed for conditional styling. Understanding these CSS techniques complements our guide on CSS styling methods for building maintainable interfaces.

Sources

1. DEV Community: The Ultimate 2025 CSS Guide
2. OpenReplay: 5 Modern CSS Features Every Developer Should Know
3. Frontend Masters: What You Need to Know about Modern CSS (2025 Edition)