Authentication in Next.js
Authentication is critical—get it wrong and you expose your users to serious risks. Here's how to do it right.
Popular Auth Options
| Solution | Best For | Complexity |
|---|---|---|
| Auth.js (NextAuth) | Most projects | Low |
| Clerk | Quick setup, managed | Low |
| Supabase Auth | If using Supabase | Low |
| Custom JWT | Full control needed | High |
Auth.js Setup Overview
- Install the package
- Configure providers (Google, GitHub, Credentials)
- Set up database adapter (Prisma recommended)
- Create API route handler
- Wrap app with SessionProvider
Protecting Routes
Server Component Protection
- Use getServerSession() to check auth
- Redirect unauthorized users
- Keep sensitive data server-side
Middleware Protection
- Protect entire route groups
- Check auth before page loads
- Configure matcher patterns
Security Best Practices
1. Password Hashing
- Always use bcrypt with cost factor 12+
- Never store plain text passwords
- Use constant-time comparison
2. CSRF Protection
- Auth.js handles this automatically
- Always validate CSRF tokens
- Use SameSite cookie attribute
3. Secure Cookies
- HttpOnly: true (prevent XSS access)
- Secure: true (HTTPS only)
- SameSite: lax or strict
4. Rate Limiting on Auth Endpoints
- Limit login attempts (5 per 15 minutes)
- Implement exponential backoff
- Log suspicious activity
5. Input Validation
- Validate email format
- Check password strength
- Sanitize all inputs
Common Vulnerabilities to Avoid
- Storing passwords in plain text - Always hash
- Session fixation - Regenerate session on login
- No rate limiting - Enable on auth endpoints
- Exposing sensitive data in JWT - Minimal claims only
- Missing HTTPS - Always use in production
Need Help with Authentication?
Security is not something to compromise on. I build secure authentication systems for SaaS and web applications. Let's discuss your requirements.