// SvelteKit data flow guidance. Use for load functions, form actions, server/client data, and invalidation. Covers +page.server.ts vs +page.ts, serialization, fail(), redirect(), error(), invalidateAll().
| name | sveltekit-data-flow |
| description | SvelteKit data flow guidance. Use for load functions, form actions, server/client data, and invalidation. Covers +page.server.ts vs +page.ts, serialization, fail(), redirect(), error(), invalidateAll(). |
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 query(), form(), command(), and prerender() patterns in .remote.ts files.
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, or migration. Covers $state, $derived, $effect, $props, $bindable. Prevents reactivity mistakes.
Svelte CSS styling patterns. Use for scoped styles, CSS custom properties, style: directive, :global, or styling child components.
SvelteKit structure guidance. Use for routing, layouts, error handling, SSR, or svelte:boundary. Covers file naming, nested layouts, error boundaries, pending UI, and hydration.