Protecting Your Routes and Data with Supabase Auth | Authentication Made Simple with Supabase Auth | Supabase Made Easy: Your First Steps to Building with Open Source Firebase Alternative

You've successfully set up user authentication with Supabase Auth! Now, the crucial next step is to secure your application. This means ensuring that only authenticated users can access certain routes or view sensitive data. Supabase makes this remarkably straightforward.

At its core, protecting your routes and data involves checking the user's authentication status before granting access. Supabase provides a simple way to access the currently logged-in user's information and leverage this in your application logic.

The Supabase JavaScript client offers a convenient user object which is null if no user is authenticated, and an object containing user details if they are logged in. We can use this to conditionally render components or redirect unauthenticated users.

import { supabase } from './supabaseClient';

function ProtectedComponent() {
  const [user, setUser] = React.useState(null);

  React.useEffect(() => {
    const { data: authListener } = supabase.auth.onAuthStateChange(
      (_event, session) => {
        setUser(session?.user || null);
      }
    );

    return () => {
      authListener.subscription.unsubscribe();
    };
  }, []);

  if (!user) {
    return <p>Please sign in to view this content.</p>;
  }

  return <p>Welcome, {user.email}! This is protected content.</p>;
}

This code snippet demonstrates a common pattern: listening for authentication state changes. When the authentication state changes (e.g., user signs in or out), we update our component's user state. Then, we conditionally render the protected content only if user is not null.

Beyond frontend protection, you'll want to secure your data in Supabase itself. This is where Row Level Security (RLS) comes into play, a powerful feature that allows you to define fine-grained access control directly within your database tables.

When RLS is enabled on a table, Supabase applies policies to every database query. These policies can dictate who can SELECT, INSERT, UPDATE, or DELETE rows based on the authenticated user's identity and other conditions. Your backend code then interacts with the database as usual, and RLS ensures only permitted operations succeed.