How does SvelteKit handle API routes?

SvelteKit API routes are created by adding +server.js files in the routes directory. Export named functions corresponding to HTTP methods: export async function GET({ params, url }) { const data = await db.query(params.id); return new Response(JSON.stringify(data), { headers: { 'Content-Type': 'application/json' } }); }. Alternatively, use the built-in json() helper: import { json } from '@sveltejs/kit'; return json(data);. Handle POST: export async function POST({ request }) { const body = await request.json(); ... }. Error responses: import { error } from '@sveltejs/kit'; throw error(404, 'Not found');. API routes support GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS. They share the hooks infrastructure (authentication via event.locals). Unlike form actions (for form submissions), API routes are for programmatic API access from client-side JavaScript or external clients.