Loaders

Official docs: Loaders

Loaders are server-side data fetching functions that run before rendering. They are tree-shaken from the client bundle — database queries, API keys, and server logic never reach the browser.

When to Use

• Fetching data for a page (database, external API, filesystem)
• Server-side authentication checks and redirects
• Setting response headers (caching, cookies)
• File-driven content (MDX, JSON) with hot reload

When NOT to Use

• Client-side interactions (button clicks, form submissions) — use API routes
• Real-time data — use client-side fetching or websockets after initial load

Basic Usage