Rethinking 'rethinking reactivity'. Svelte 5 introduces runes — compiler signals that drive reactivity. Key runes include $state, $derived, $effect, and $props. Runes work across .svelte and .svelte.js/.svelte.ts files, replacing the let/$: reactive model from Svelte 4. Also replaces stores with universal reactive state.
Fetched May 1, 2026