Authentication Patterns

Architectural approaches to handling user sessions and protected routes in the App Router.

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Next.js Authentication Patterns

Authentication in Next.js (especially the App Router) revolves around where the session is stored and how it is accessed.

Session Strategies

  1. Server-side Sessions (HTTP-only Cookies): The preferred method for security. Sessions are read in Middleware, Server Components, and Route Handlers.
  2. Client-side Sessions (JWT in LocalStorage): Less secure and generally discouraged in modern Next.js apps as they can’t be accessed by Server Components during pre-rendering.

Protection Mechanisms

  • Middleware: The first line of defense. Used to redirect unauthenticated users before they even reach a page.
  • Server Components: Checking for a session directly using cookies() or a library like Auth.js to conditionally render content.
  • Route Handlers/Actions: Validating the session before performing any sensitive mutations.