// SvelteKit data flow guidance. Use for load functions, form actions, and server/client data. Covers +page.server.ts vs +page.ts, serialization, fail(), redirect(), error().
| name | sveltekit-data-flow |
| description | SvelteKit data flow guidance. Use for load functions, form actions, and server/client data. Covers +page.server.ts vs +page.ts, serialization, fail(), redirect(), error(). |
Which file? Server-only (DB/secrets): +page.server.ts |
Universal (runs both): +page.ts | API: +server.ts
Load decision: Need server resources? → server load | Need client APIs? → universal load
Form actions: Always +page.server.ts. Return fail() for
errors, throw redirect() to navigate, throw error() for failures.
// +page.server.ts
import { fail, redirect } from '@sveltejs/kit';
export const load = async ({ locals }) => {
const user = await db.users.get(locals.userId);
return { user }; // Must be JSON-serializable
};
export const actions = {
default: async ({ request }) => {
const data = await request.formData();
const email = data.get('email');
if (!email) return fail(400, { email, missing: true });
await updateEmail(email);
throw redirect(303, '/success');
},
};
data param | ALWAYS
throw redirect()/error()SvelteKit remote functions guidance. Use for command(), query(), form() patterns in .remote.ts files.
Research topics by verifying actual source content. Use when asked to research or study links and documentation.
Svelte component patterns. Use for web components, component libraries (Bits UI, Ark UI, Melt UI), form patterns, or third-party integration.
Svelte deployment guidance. Use for adapters, Vite config, pnpm setup, library authoring, PWA, or production builds.
Svelte runes guidance. Use for reactive state, props, effects, attachments, or migration. Covers $state, $derived, $effect, @attach. Prevents reactivity mistakes.
SvelteKit structure guidance. Use for routing, layouts, error handling, SSR, or svelte:boundary. Covers file naming, nested layouts, error boundaries, pending UI, and hydration.