Optimizing Lottie Animations with CSS Preloading: A Practical Approach

When enhancing website interactivity, lightweight animations like Lottie can be incredibly effective. However, developers often encounter challenges with smooth playback and initial load performance, especially when trying to preload animation frames to ensure seamless user experience.

In this post, we explore an example from a personal project where a Lottie animation simulating a 3D rotate effect on energy cans is used to create engaging hover interactions. The goal was to eliminate initial flickering and layout shifts by preloading image frames, but traditional methods proved insufficient.

The Challenge

The project, originally built in Webflow, was recreated using HTML, CSS, and JavaScript to gain greater control. The primary issue involved the first hover event: upon first interaction, all the image frames needed for the animation loaded simultaneously, causing a noticeable blinking effect and shifting layout. Attempts to trigger the animation preemptively with JavaScript did not resolve the problem, leaving a less-than-ideal user experience.

Why Preloading Matters

Preloading animation frames ensures that when a user interacts with the element, the frames are readily available, resulting in smooth transitions. Without effective preloading, the animation jitters or delays, which can detract from the site’s professionalism and user engagement.

Exploring Solutions

While replacing Lottie with pure CSS animations is one strategy, it often falls short for complex 3D effects. Instead, a more reliable approach involves preloading the individual image frames used in the animation sequence. Techniques include:

• Using JavaScript to load all image frames into memory before user interaction.
• Employing CSS sprites or background image techniques to minimize HTTP requests.
• Ensuring images are cached effectively to reduce load times on subsequent interactions.

Practical Implementation

In the specific case referenced, preloading the image frames involved iterating through the frame URLs and loading them into the browser cache during page load or on a designated preloading event. This way, when the hover occurs, the frames are instantly available, resulting in fluid animation without flickering or layout shifts.

Further Resources

For a live example of the project and to see the implementation in action, visit: https://mitchangus.design/LiftOff

Conclusion

Preloading image frames is vital for delivering smooth, immersive animations, especially when working with frame-by-frame sequences or Lottie files. While it may require a bit