SvelteKit Has a Free API: Full-Stack JavaScript Without the React Tax

React developers spend half their time fighting React. SvelteKit developers spend that time building features.

What Is SvelteKit?

SvelteKit is the full-stack framework for Svelte — think Next.js but for Svelte. It gives you server-side rendering, API routes, file-based routing, form actions, streaming, and edge deployment.

Unlike Next.js, it compiles away the framework. Your users download plain JavaScript, not a runtime.

The API Routes

SvelteKit's +server.js files are API endpoints:

// src/routes/api/users/+server.ts
import { json } from '@sveltejs/kit';

export async function GET({ url }) {
  const limit = Number(url.searchParams.get('limit') ?? 10);
  const users = await db.user.findMany({ take: limit });
  return json(users);
}

export async function POST({ request }) {
  const { name, email } = await request.json();
  const user = await db.user.create({ data: { name, email } });
  return json(user, { status: 201 });
}

Form Actions: The Killer Feature

Forget useState, onSubmit, e.preventDefault():

// src/routes/login/+page.server.ts
export const actions = {
  default: async ({ request, cookies }) => {
    const data = await request.formData();
    const user = await authenticate(data.get('email'), data.get('password'));
    if (!user) return fail(401, { incorrect: true });
    cookies.set('session', user.token, { path: '/' });
    throw redirect(303, '/dashboard');
  }
};

No JavaScript on the client needed. Works without JS. Progressively enhanced.

Why Developers Are Switching

1. Bundle size — SvelteKit apps ship 40-60% less JavaScript than Next.js equivalent.

2. No hydration mismatch — Svelte compiles components, so server and client always agree.

3. Simplicity — $: reactive statements vs useEffect + useState + useCallback + useMemo.

4. Speed — Svelte 5 with runes is the fastest mainstream UI framework in benchmarks.

A startup rebuilt their Next.js marketing site in SvelteKit: bundle 340KB to 120KB, Lighthouse 72 to 98, build time 45s to 12s.

npx sv create my-app && cd my-app && npm run dev

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