Svelte 5 Runes

Svelte 5 introduces runes—compiler-driven reactivity primitives that replace Svelte 4's implicit reactivity. Runes provide fine-grained, predictable reactivity that works in .svelte and .svelte.ts files.

Core Runes

$state - Reactive State

Declare reactive state that triggers updates when changed:

<script>
  let count = $state(0);
  let user = $state({ name: 'Alice', age: 30 });
</script>

<button onclick={() => count++}>{count}</button>