Do Animations Slow Down Your Website?

Yes, animations can slow a website, but a well-built one usually will not. What matters most is which property you animate. Moving an element with transform or opacity stays smooth, because the browser offloads that work to the compositor. Animating an element's size or position instead forces the page to recalculate its layout, sometimes 60 times a second. That constant recalculation is what makes a site feel laggy.

What actually slows a page down

The slowdown comes from what an animation forces the browser to recompute, not from motion itself. Google's guidance on animation performance advises that you restrict animations to opacity and transform, so they stay on the compositing step.

Animate width, height, top, or left instead, and the browser has to redo layout and repaint. It repeats that work for every frame.

As the same guide puts it, an animation that moves an element with anything other than transform is likely to be slow.

Animate this	Cost	Why
transform, opacity	Low	Stays on the compositor, off the layout path
width, height, margin	High	Forces the browser to redo layout
top, left, box-shadow	High	Triggers repaint on every frame

The practical rule is short. If you can express a movement as a transform, do, and most movements can be.

How animation shows up in Core Web Vitals

Animation touches two of Google's Core Web Vitals, layout stability and responsiveness. Content that jumps as it animates hurts Cumulative Layout Shift, where a good score is 0.1 or less (Google, web.dev, updated April 2023).

Heavy animation that ties up the main thread can delay a tap. That is measured by Interaction to Next Paint, where good is 200 milliseconds or less.

An animation that reflows the layout as it plays is exactly the kind that pushes the layout-shift score the wrong way. A composited transform avoids that, because it does not move the content around it.

In our experience, a site's performance quietly degrades as content and images pile up. A page thick with scripts and effects is often where we start looking when a site feels slow.

Respecting people who want less motion

Fast is not the only goal, because some visitors need less motion outright. Browsers expose that choice through the prefers-reduced-motion media feature, which detects when someone has asked their device to minimize non-essential motion.

Honor it by cutting decorative movement, parallax included, when the setting is on. MDN notes that such animations can trigger discomfort for people with vestibular motion disorders.

Because that setting travels with the device, motion is part of responsive design thinking. Respecting it is a web accessibility basic, not a nicety.

Auto-playing motion has a hard rule

Motion that starts on its own and runs a while has an accessibility rule attached. WCAG's Pause, Stop, Hide criterion is a Level A requirement.

Anything moving that starts automatically, lasts more than five seconds, and runs alongside other content must give the visitor a way to pause, stop, or hide it. Auto-rotating carousels and looping background videos are the usual offenders.

Frequently asked questions

Do CSS animations slow a website more than JavaScript ones?

Not inherently, because what matters is the property you animate, not the language. A CSS animation on transform and a JavaScript one on transform are both light to render.

A JavaScript animation that changes width or position on every frame is expensive, and so is the CSS version. Choose the property first; the technology is secondary. Well-built CSS transitions are usually the simplest performant option.

Does removing animations speed up my site?

It can, if the animations were the heavy kind that force layout or repaint. Removing a transform-based effect saves almost nothing, because it was light already. The bigger wins usually come from images, fonts, and third-party scripts, not from motion. A forced loading screen is the one effect worth removing outright. Measure with a tool like PageSpeed Insights before you strip effects, so you cut what actually costs you.

Are website animations bad for SEO?

Not directly, because search engines rank content, not motion. The indirect risk is speed. Animations that hurt Core Web Vitals can drag on rankings and lose impatient visitors. Light, composited animation has no real SEO cost. The issue is only ever a slow page, so keep effects off the layout path and your SEO stays unaffected.

What is the most performance-friendly way to animate?

Animate transform and opacity, and let the browser handle them on the compositor. Use them for movement, scaling, rotation, and fades, which covers most interface animation. Avoid animating width, height, top, left, or box-shadow, since each forces layout or repaint on every frame. When you need one of those, check whether a transform can produce the same visual result.

Do animations affect mobile performance more?

Yes, usually, because a phone has less processing power than a laptop. An animation that runs smoothly on your desktop can stutter on a mid-range Android phone. Test on a real, modest phone, not just a fast machine. Keeping animation on transform and opacity is what keeps it smooth on weaker hardware.

Should I remove all animation for accessibility?

No, because tasteful motion can aid understanding, like a smooth transition that shows where a panel came from. The rule is to respect the visitor's choice. Cut decorative motion when prefers-reduced-motion is set, and meet Pause, Stop, Hide for anything that auto-plays past five seconds. Motion a visitor controls, and can switch off, is not an accessibility problem.

Motion that does not cost speed

Storming Solutions builds custom-coded websites for Malaysian businesses from Kuala Lumpur, and runs SEO, AEO, and GEO. We use animation to guide attention and confirm actions, built on the properties that stay off the layout path, so a site stays fast on a modest phone.

Our honest view is that most performance problems are not the animation, they are the images and scripts around it. Wondering why your site feels slow? Talk to us about web development, and we will find what is actually costing you speed.