Supabase Auth

Supabase Authentication

Cookie-based authentication with SSR support.

When to Use This Skill

• Need authentication without rolling your own
• Building a Next.js app with SSR
• Want email/password + social auth options
• Need automatic session refresh

Core Concepts

1. Browser client - For client components
2. Server client - For API routes and server components
3. Cookie-based sessions - Automatic refresh via middleware
4. User profiles - Extended user data in your database

TypeScript Implementation

Browser Client

// lib/supabase.ts
import { createBrowserClient } from '@supabase/ssr';

export function createClient() {
  return createBrowserClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
  );
}

Server Client

// lib/supabase-server.ts
import { createServerClient, type CookieOptions } from '@supabase/ssr';
import { cookies } from 'next/headers';

export async function createServerSupabaseClient() {
  const cookieStore = await cookies();

  return createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      cookies: {
        getAll() {
          return cookieStore.getAll();
        },
        setAll(cookiesToSet: { name: string; value: string; options: CookieOptions }[]) {
          try {
            cookiesToSet.forEach(({ name, value, options }) =>
              cookieStore.set(name, value, options)
            );
          } catch {
            // Called from Server Component - ignore
          }
        },
      },
    }
  );
}

Login Page

// app/login/page.tsx
'use client';

import { useState } from 'react';
import { useRouter, useSearchParams } from 'next/navigation';
import { createClient } from '@/lib/supabase';

export default function LoginPage() {
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [error, setError] = useState<string | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  
  const router = useRouter();
  const searchParams = useSearchParams();
  const redirectTo = searchParams.get('redirectTo') || '/dashboard';
  const supabase = createClient();

  const handleLogin = async (e: React.FormEvent) => {
    e.preventDefault();
    setError(null);
    setIsLoading(true);

    try {
      const { error } = await supabase.auth.signInWithPassword({
        email,
        password,
      });

      if (error) throw error;

      router.push(redirectTo);
      router.refresh();
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Login failed');
    } finally {
      setIsLoading(false);
    }
  };

  return (
    <form className="space-y-4 max-w-md mx-auto mt-20">
      <h1 className="text-2xl font-bold">Sign In</h1>
      
      <input
        type="email"
        value={email}
        => setEmail(e.target.value)}
        placeholder="Email"
        required
        className="w-full px-4 py-2 border rounded"
      />
      
      <input
        type="password"
        value={password}
        => setPassword(e.target.value)}
        placeholder="Password"
        required
        className="w-full px-4 py-2 border rounded"
      />
      
      {error && (
        <div className="p-3 bg-red-100 text-red-700 rounded">{error}</div>
      )}
      
      <button
        type="submit"
        disabled={isLoading}
        className="w-full py-2 bg-blue-600 text-white rounded disabled:opacity-50"
      >
        {isLoading ? 'Signing in...' : 'Sign In'}
      </button>
      
      <p className="text-center text-sm">
        Don't have an account? <a href="/signup" className="text-blue-600">Sign up</a>
      </p>
    </form>
  );
}

Signup Page

// app/signup/page.tsx
'use client';

import { useState } from 'react';
import { createClient } from '@/lib/supabase';

export default function SignupPage() {
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [name, setName] = useState('');
  const [error, setError] = useState<string | null>(null);
  const [success, setSuccess] = useState(false);
  const [isLoading, setIsLoading] = useState(false);

  const handleSignup = async (e: React.FormEvent) => {
    e.preventDefault();
    setError(null);
    setIsLoading(true);

    try {
      const supabase = createClient();
      
      const { data, error: signUpError } = await supabase.auth.signUp({
        email,
        password,
        options: {
          data: { display_name: name },
          emailRedirectTo: `${window.location.origin}/auth/callback`,
        },
      });

      if (signUpError) throw signUpError;

      if (data?.user?.identities?.length === 0) {
        setError('This email is already registered.');
        return;
      }

      setSuccess(true);
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Signup failed');
    } finally {
      setIsLoading(false);
    }
  };

  if (success) {
    return (
      <div className="text-center mt-20">
        <h1 className="text-2xl font-bold mb-4">Check your email</h1>
        <p>We sent a confirmation link to {email}</p>
      </div>
    );
  }

  return (
    <form className="space-y-4 max-w-md mx-auto mt-20">
      <h1 className="text-2xl font-bold">Create Account</h1>
      
      <input
        type="text"
        value={name}
        => setName(e.target.value)}
        placeholder="Name"
        className="w-full px-4 py-2 border rounded"
      />
      
      <input
        type="email"
        value={email}
        => setEmail(e.target.value)}
        placeholder="Email"
        required
        className="w-full px-4 py-2 border rounded"
      />
      
      <input
        type="password"
        value={password}
        => setPassword(e.target.value)}
        placeholder="Password (min 6 characters)"
        minLength={6}
        required
        className="w-full px-4 py-2 border rounded"
      />
      
      {error && (
        <div className="p-3 bg-red-100 text-red-700 rounded">{error}</div>
      )}
      
      <button
        type="submit"
        disabled={isLoading}
        className="w-full py-2 bg-blue-600 text-white rounded disabled:opacity-50"
      >
        {isLoading ? 'Creating account...' : 'Create Account'}
      </button>
    </form>
  );
}

Auth Callback Route

// app/auth/callback/route.ts
import { createServerClient } from '@supabase/ssr';
import { cookies } from 'next/headers';
import { NextResponse } from 'next/server';

export async function GET(request: Request) {
  const { searchParams, origin } = new URL(request.url);
  const code = searchParams.get('code');
  const next = searchParams.get('next') ?? '/dashboard';

  if (code) {
    const cookieStore = await cookies();
    
    const supabase = createServerClient(
      process.env.NEXT_PUBLIC_SUPABASE_URL!,
      process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
      {
        cookies: {
          getAll() {
            return cookieStore.getAll();
          },
          setAll(cookiesToSet) {
            cookiesToSet.forEach(({ name, value, options }) =>
              cookieStore.set(name, value, options)
            );
          },
        },
      }
    );

    const { error } = await supabase.auth.exchangeCodeForSession(code);
    
    if (!error) {
      return NextResponse.redirect(`${origin}${next}`);
    }
  }

  return NextResponse.redirect(`${origin}/login?error=auth_callback_error`);
}

useUser Hook

// hooks/useUser.ts
'use client';

import { useEffect, useState, useCallback } from 'react';
import { createClient } from '@/lib/supabase';
import type { User } from '@supabase/supabase-js';

interface UserProfile {
  id: string;
  display_name: string | null;
  subscription_tier: 'free' | 'pro';
}

export function useUser() {
  const [user, setUser] = useState<User | null>(null);
  const [profile, setProfile] = useState<UserProfile | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const supabase = createClient();

  const fetchProfile = useCallback(async (userId: string) => {
    const { data } = await supabase
      .from('user_profiles')
      .select('*')
      .eq('id', userId)
      .single();
    return data as UserProfile | null;
  }, [supabase]);

  const signOut = useCallback(async () => {
    await supabase.auth.signOut();
    setUser(null);
    setProfile(null);
  }, [supabase]);

  useEffect(() => {
    const getSession = async () => {
      const { data: { session } } = await supabase.auth.getSession();
      
      if (session?.user) {
        setUser(session.user);
        const profileData = await fetchProfile(session.user.id);
        setProfile(profileData);
      }
      setIsLoading(false);
    };

    getSession();

    const { data: { subscription } } = supabase.auth.onAuthStateChange(
      async (event, session) => {
        if (event === 'SIGNED_IN' && session?.user) {
          setUser(session.user);
          const profileData = await fetchProfile(session.user.id);
          setProfile(profileData);
        } else if (event === 'SIGNED_OUT') {
          setUser(null);
          setProfile(null);
        }
      }
    );

    return () => subscription.unsubscribe();
  }, [supabase, fetchProfile]);

  return {
    user,
    profile,
    tier: profile?.subscription_tier ?? 'free',
    isLoading,
    signOut,
  };
}

Database Migration

-- migrations/001_user_profiles.sql

CREATE TABLE user_profiles (
    id UUID PRIMARY KEY REFERENCES auth.users(id) ON DELETE CASCADE,
    display_name VARCHAR(255),
    subscription_tier VARCHAR(20) NOT NULL DEFAULT 'free',
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Auto-create profile on signup
CREATE OR REPLACE FUNCTION handle_new_user()
RETURNS TRIGGER AS $$
BEGIN
    INSERT INTO user_profiles (id, display_name)
    VALUES (NEW.id, NEW.raw_user_meta_data->>'display_name');
    RETURN NEW;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;

CREATE TRIGGER on_auth_user_created
    AFTER INSERT ON auth.users
    FOR EACH ROW EXECUTE FUNCTION handle_new_user();

-- RLS
ALTER TABLE user_profiles ENABLE ROW LEVEL SECURITY;

CREATE POLICY "Users can view own profile" ON user_profiles
    FOR SELECT USING (auth.uid() = id);

CREATE POLICY "Users can update own profile" ON user_profiles
    FOR UPDATE USING (auth.uid() = id);

Best Practices

1. Use SSR client - Server components need cookie access
2. Refresh in middleware - Keep sessions alive automatically
3. Auto-create profiles - Database trigger on signup
4. Enable RLS - Row-level security on all user tables
5. Handle email confirmation - Check for empty identities array

Common Mistakes

• Using browser client in server components
• Not refreshing session in middleware
• Missing RLS policies on user data
• Not handling email confirmation flow
• Forgetting to call router.refresh() after login

Related Skills

• Middleware Protection
• Row Level Security
• JWT Auth