Implementing Authentication in Next.js
To add authentication to your Next.js application, grasp these core concepts:
Key Concepts
- Authentication: Verifies user identity (e.g., username/password or via Google).
- Session Management: Tracks user's state across requests.
- Authorization: Controls access to different parts of the app.
Authentication Strategies
- OAuth/OpenID Connect (OIDC): Ideal for social logins and Single Sign-On (SSO).
- Email + Password: Common and straightforward, requires strong security.
- Passwordless: Uses email magic links or SMS codes, reducing password fatigue.
- Passkeys/WebAuthn: High-security cryptographic credentials, complex to implement.
Implementing Email-Password Authentication
Here’s how to add basic email-password authentication to a Next.js app:
Login Form
Create a login form in app/login/page.tsx:
import { authenticate } from '@/app/lib/actions';
export default function Page() {
return (
<form action={authenticate}>
<input type="email" name="email" placeholder="Email" required />
<input type="password" name="password" placeholder="Password" required />
<button type="submit">Login</button>
</form>
);
}
Authentication Logic
Handle authentication in app/lib/actions.ts:
'use server';
import { signIn } from '@/auth';
export async function authenticate(formData: FormData) {
try {
await signIn('credentials', formData);
} catch (error) {
if (error) {
switch (error.type) {
case 'CredentialsSignin':
return 'Invalid credentials.';
default:
return 'Something went wrong.';
}
}
throw error;
}
}
Form Handling
Manage form state and handle errors in app/login/page.tsx:
'use client';
import { authenticate } from '@/app/lib/actions';
import { useFormState, useFormStatus } from 'react-dom';
export default function Page() {
const [errorMessage, dispatch] = useFormState(authenticate, undefined);
return (
<form action={dispatch}>
<input type="email" name="email" placeholder="Email" required />
<input type="password" name="password" placeholder="Password" required />
{errorMessage && <p>{errorMessage}</p>}
<LoginButton />
</form>
);
}
function LoginButton() {
const { pending } = useFormStatus();
return (
<button aria-disabled={pending} type="submit">
Login
</button>
);
}
Conclusion
This setup provides a basic email-password authentication flow. For enhanced security and multiple login options, consider integrating OAuth or passwordless authentication methods.
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