Animations are often the secret ingredient that turns a static, lifeless web page into a delightful and interactive experience. From subtle hover effects to more sophisticated UI transitions, they help guide users, grab attention, and enhance usability. However, without careful planning and execution, animations can become a major bottleneck for performance, especially when it comes to metrics like INP (Interaction to Next Paint). High INP scores mean users experience laggy interactions, which can seriously impact user satisfaction and SEO rankings.

So how do you strike the balance between dynamic design and silky-smooth responsiveness? In this article, we’ll explore how to approach web animations in a performance-friendly way that doesn’t compromise your site’s INP score.

Understanding INP: A Quick Refresher

INP, or Interaction to Next Paint, is a web performance metric introduced by Google as part of its Core Web Vitals initiative. It measures the responsiveness of a web page by analyzing the delay between a user interaction and the visual response in the UI. While it considers many interactions, INP focuses especially on the longest latency interaction in a session, meaning even one sluggish moment can result in a poor score.

Animations, especially the unoptimized ones, are often the cause of high latency during interactions. They can hog the main thread, induce style and layout recalculations, or trigger repaints that lead to jank and lag.

Why Animations Affect INP

At the core of rendering web animations is the browser’s main thread, responsible for:

• Handling user input
• Calculating layouts
• Painting pixels onto the screen

When animations are not optimized, they compete for the same resources as user interaction handlers. This overlap can cause the browser to delay the UI response because it’s busy rendering something else.

There’s also the issue of layout thrashing—where rapid, non-sequential reads and writes to the DOM force the browser to repeatedly recalculate layouts on the fly. This kind of inefficiency doesn’t just degrade performance; it kills responsiveness.

High-Performance Animation Strategies

Let’s dive into practical strategies for creating animations that look great and respect your INP score.

1. Animate Only Composite Properties

This is probably the golden rule of performant animations. Not all CSS properties are created equal. Some trigger heavy rendering costs, while others are inexpensive because they can be offloaded to the GPU.

Stick to animating these “safe” properties:

• transform – like translate, scale, rotate
• opacity

These can be handled by the compositor thread, bypassing reflows and repaints. Avoid animating properties like top, left, height, and width, as these require recalculating layout, which is a costly operation.

2. Use the FLIP Technique

FLIP stands for First, Last, Invert, Play—a strategy for animating layout changes without causing layout thrashing. It involves the following steps:

1. First: Capture the element’s initial position.
2. Last: Apply your final layout changes and grab the new position.
3. Invert: Compute the difference between the two states and animate it using transforms.
4. Play: Smoothly animate from the inverted transform back to its natural position.

This bypasses layout recalculations during the animation itself, letting the GPU take the wheel for a smooth and snappy experience.

3. Avoid JavaScript for Heavy Animations

JavaScript has its place, especially for complex interactions, but it shouldn’t be the go-to for high-frequency animation loops (like scroll-based animations or frame-by-frame moves). JavaScript can easily block the main thread if not handled properly.

When you do use JS for animations, use APIs like:

• requestAnimationFrame() – syncs with display refresh for 60fps gain
• Web Animations API – efficient and less blocking than manually manipulating styles

Prefer CSS transitions and animations whenever possible. They are declarative, off the main thread, and better optimized by most modern browsers.

4. Debounce Expensive Handlers

If animations are triggered by scroll, mousemove, resize, or other frequent events, make sure to debounce or throttle them. This prevents them from firing dozens of times per second, which can lead to DOM bottlenecks and high INP latency.

Use libraries like Lodash, which offer simple debounce() and throttle() utilities, or implement your own if your needs are simple.

5. Preload and Cache Animation Assets

Heavy video backgrounds or Lottie animations can cause momentary freezes when loaded near interaction time. Use <link rel="preload"> to get asset pipelines running before user interactions start. For JSON-based animations, consider converting them into spritesheets or use tools that bake animations into frame sequences hosted on a CDN.

6. Monitor and Measure

Even the best strategies need validation. Use performance tools to inspect how your animations affect INP in practice:

• Chrome DevTools → Performance tab: Find frames where user interaction overlaps with animation execution.
• Lighthouse: Run audits and specifically check the INP numbers.
• Web Vitals Chrome Extension: Track INP in real time as you interact with the page.

Also, investigate usage patterns. If an animation is rarely seen or interacted with, you might not need it at all—or it can be deferred.

Progressively Enhanced Animations

It’s important to deliver the right experience to the right user setup. Consider fallback mechanisms or disabling large animations entirely for users on low-end devices or slow networks.

Use prefers-reduced-motion media query to respect user preferences:

@media (prefers-reduced-motion: reduce) {
  * {
    animation: none !important;
    transition: none !important;
  }
}

This ensures that you’re not harming accessibility in the pursuit of flair.

Animation Libraries That Respect INP

Many modern animation libraries are designed with performance in mind. Here are a few that can help you build responsive animations:

• Framer Motion (React) – declarative, well-optimized transitions and gestures
• GSAP – highly customizable, robust performance tuning
• Motion One – ultra-light, targeting GPU-accelerated properties only

These tools abstract a lot of performance pitfalls and come with smart defaults. Just make sure not to overload any library with simultaneous animations—that’s a surefire way to spike INP metrics.

Real-World Examples: Learning from the Pros

Companies that prioritize web performance often take a hybrid approach to animation. For instance:

• Stripe uses GPU-friendly animations for their onboarding UI and payment flows, keeping it fast and elegant.
• Apple leans heavily into native-feeling transitions using minimalistic animations designed for speed.
• Notion features subtle animated interactions like list reordering, all implemented using performant CSS transitions and FLIP logic.

Each of these companies invests in performance monitoring and continuously optimizes based on real user feedback.

Conclusion: Design with INP in Mind

Web animations are not the enemy of performance—but poor animation practices are. When thoughtfully implemented with modern techniques that prioritize GPU-accelerated properties, reduce main thread reliance, and respond to user intent, animations can shine without harming responsiveness.

As web standards continue to evolve and INP becomes a standard metric, designers and developers should stay informed and strike the perfect balance between beauty and speed. After all, a smooth interaction is just as memorable as a beautiful interface. Or perhaps, it’s what makes beauty usable to begin with.