Optimizing Lottie Animations with CSS Preloading: A Developer’s Approach

When transitioning from Webflow to a custom HTML, CSS, and JavaScript setup, many developers encounter challenges with animation performance and user experience. One common issue involves ensuring that animated image sequences, such as those used to simulate 3D rotations via Lottie animations, preload efficiently to prevent flickering or layout shifts upon user interaction.

In a recent project, I aimed to replicate a hover-based 3D rotation effect on energy cans, originally created with a Lottie animation, but I wanted to replace it with pure CSS for better control and performance. However, I faced a hurdle: preloading the individual frames that compose the animation to ensure smooth playback without delays or visual glitches.

The core problem was that, on the initial hover, all image frames loaded simultaneously, causing undesirable blinking and layout jumps. Attempting to preload by triggering the animation once during page load using JavaScript didn’t resolve the issue. The goal was to have all frames ready before the user hovers, creating a seamless experience.

Here’s the project for reference:
https://mitchangus.design/LiftOff

Key Observations and Solutions:

• Preloading Assets: Ensuring all image frames are loaded into the browser’s cache before user interaction is crucial. This can be achieved by programmatically preloading images upon page load using JavaScript, which helps eliminate delays during hover.

• CSS Sprites or Multiple Images: Instead of loading individual images on hover, consolidating frames into a single sprite sheet or preloading all images can provide smoother transitions. Using CSS background-position shifts can eliminate the need for multiple image loads during interaction.

• JavaScript Preloading Technique: Implement a script that creates new Image objects for each frame and sets their src attributes during page load. Once all images are loaded, subsequent animations can run smoothly without additional latency.

• Avoiding Layout Shifts: To prevent layout shifts, set explicit image or container dimensions, and consider using CSS containment properties. Preloading images and controlling their visibility can maintain layout stability.

Summary

Replacing a Lottie animation with CSS and images can offer performance improvements but requires careful planning around asset preloading. By proactively loading all frames before user interaction, developers can deliver a fluid and professional experience without flickers or jumps. This approach involves a combination of JavaScript preloading techniques and CSS strategies such as sprites or absolute