Boost Your UI with On-Demand CSS Libraries

Jun 19, 2025 - 2 min read

Dynamic CSS Library Injection: Enhanced UI Without the Wait

CSS libraries like Animate.css, Bootstrap, or Bulma can add powerful styling and animation capabilities to your site. However, loading these libraries upfront can significantly increase your initial page load time—especially when their features might only be needed for specific interactions.

The Smart Approach: Load CSS Libraries On-Demand

With Boostify’s content injection capabilities, you can load CSS libraries dynamically, exactly when you need them:

(async () => {
    try {
        // Load Animate.css when user interacts with a specific element
        document.getElementById('show-animation').addEventListener('click', async () => {
            await bstf.loadStyle({
                url: 'https://cdnjs.cloudflare.com/ajax/libs/animate.css/4.1.1/animate.min.css',
                appendTo: 'head',
                attributes: ["id=animate-css"],
            });
            console.log('Animate.css loaded successfully.');

            // Now you can apply animation classes
            document.getElementById('animated-element').className += ' animate__animated animate__bounce';
        });

    } catch (error) {
        console.error(error);
    }
})();

The Benefits Are Clear

Faster Initial Page Load: Your core content loads quickly without being delayed by non-essential CSS.
Better Performance Metrics: Improve Core Web Vitals by deferring non-critical resources.
On-Demand Effects: Apply sophisticated animations and styles exactly when you need them.

Real-World Use Cases

Product Showcases: Load animation libraries when a user views product details
Interactive Tutorials: Inject styling for tutorial steps only when a user reaches that section
Form Validation: Load form-specific styling only when a user begins interacting with a form

Before and After Example

Before: A static product card with basic styling.

After: After clicking “View Details”, Animate.css is loaded and applied:

The product image scales up with animate__zoomIn
Feature highlights fade in with animate__fadeInRight
The “Add to Cart” button pulses with animate__pulse

Implementation Tips

Group related CSS libraries to minimize the number of separate requests
Consider preloading libraries for critical user paths where you know they’ll be needed
Use feature detection to load alternative libraries based on browser capabilities

By loading CSS libraries dynamically, you can create rich, engaging user experiences without compromising on initial page load performance.