# +layout.server.ts Definition
**Definition:** Server-only layout module exporting a `load` that runs
on the server for a layout segment. Useful for auth checks and shared
server data.
**Syntax:** `src/routes/(...)/+layout.server.ts` (or `.js`)
**Exports:**
- `export const load: LayoutServerLoad` — server-only loader (must
return serializable data)
- Page options: `prerender`, `ssr`, `csr` defaults for children
**Returns:** Data merges downward to child layouts and pages.
## Example
```ts
// +layout.server.ts
import type { LayoutServerLoad } from './$types';
import { error } from '@sveltejs/kit';
export const load: LayoutServerLoad = async ({ locals }) => {
if (!locals.user) throw error(401, 'not logged in');
return { user: locals.user };
};
```
## Related
- `+layout.svelte`, `+layout.ts`, `load`, `hooks.server`