Svelte 5 introduces runes for universal reactivity, snippets for reusable markup, and compiler improvements. The release includes new runes like $state, $derived, and $effect to manage state and its dependencies within components. It also offers signals and fine-grained reactivity, universal reactivity with .svelte.js files, other runes that simplify common tasks, and compiler improvements for better performance and reduced bundle sizes. Additionally, Svelte 5 introduces snippets for reusable markup and logic within a component, native TypeScript support, and benefits from Vite's growing ecosystem.