Enhance Svelte apps with reusable custom animations

Svelte’s built-in transitions like fade, fly, and slide provide instant visual appeal, but creating reusable custom animations unlocks even greater flexibility. Instead of relying solely on the framework’s defaults, developers can craft tailored effects and apply them consistently across a design system. These custom animations integrate seamlessly using Svelte’s use:, in:, and out: directives, offering cleaner syntax and automatic cleanup compared to solutions in other frameworks.

Streamlining Overlay Animations with Materialize/Dematerialize

Modals, tooltips, and toasts often require subtle enter and exit animations that avoid disrupting the page layout. The native fade transition handles opacity changes, but combining opacity, scale, blur, and vertical movement (Y) creates a smoother experience. This composite effect can be encapsulated into reusable materialize and dematerialize actions, replacing the default fade with a polished, professional transition.

{#if open}
  <div in:materialize out:dematerialize>
    Modal / tooltip / toast content
  </div>
{/if}

By defining these actions once, teams avoid reinventing the same transition logic across multiple components, reducing code duplication and improving maintainability.

Responsive Layout Shifts with Morph Transitions

Traditional enter/exit animations mount or unmount elements, which can cause abrupt layout shifts as the DOM reflows. The morph action addresses this by smoothly resizing a persistent element when its content changes, eliminating the need to toggle components. This approach preserves layout stability while providing visual feedback during state transitions.

<div use:morph={{ width: false, height: true }}>
  {#if expanded}
    <LongContent />
  {:else}
    <ShortContent />
  {/if}
</div>

Use cases include expanding accordions, collapsible sections, or dynamic charts where content length varies but the container remains.

Emerge/Dissolve for Smooth List Animations

When adding or removing items in a list, Svelte’s built-in transitions often snap into place. The emerge and dissolve actions provide a more graceful alternative by animating new elements from zero height and margin, pushing existing items downward instead of jumping. This creates a fluid, natural-feeling experience for users scrolling through dynamic lists.

{#each cards as card (card.id)}
  <div in:emerge out:dissolve>
    {card.title}
  </div>
{/each}

This pattern works particularly well for feed updates, notification lists, or any scenario where items are frequently added or removed.

Positioning-Aware Tooltips with Floating UI

Tooltips that ignore viewport boundaries frustrate users. By combining Svelte’s action system with @floating-ui/dom, developers can create tooltips that automatically reposition themselves when they near screen edges. The tooltip action handles collision detection and flips or shifts the tooltip to stay visible, while the computePosition, flip, shift, and autoUpdate utilities manage the complex positioning math.

<button use:tooltip={'Saved to your library'}>Hover me</button>

This approach reduces dependency on third-party libraries while delivering a polished user experience.

Interactive Gradient Borders for CTAs

A rotating gradient border on a call-to-action button draws attention, but it can distract users if it runs indefinitely. The laserAim action pauses the animation on hover and locks the gradient onto the cursor, creating an engaging yet controlled interaction. This subtle motion effect subtly guides users toward conversion points without overwhelming them.

<button class="btn-cta" use:laserAim>Get started</button>

Custom animations like these elevate the perceived quality of an application while keeping the implementation clean and maintainable.