SvelteKit is an open-source web application framework built on Svelte and developed by the Svelte project. Svelte renders user interface components; SvelteKit adds what a complete web app needs. Its documentation compares it to Next.js for React and to Nuxt for Vue.
At its center is a filesystem-based router: the directories under src/routes define the URL paths of the app, so src/routes/about becomes the /about page, and a folder named [slug] becomes a parameter in the URL. Rendering is configurable per part of the app: on the server (server-side rendering, SSR), in the browser (client-side rendering) or at build time (prerendering). Other features are build optimizations that load only the code a page needs, preloading of pages before the user navigates, offline support and image optimization. Development runs on Vite, which shows code changes in the browser instantly through hot module replacement. Before deployment, an adapter, a small plugin, converts the built app for a target platform; official adapters exist for Cloudflare, Netlify, Node, Bun, Vercel and static sites.
SvelteKit is free and open source under the MIT license.