Server Actions vs API Routes in Next.js: When to Use Each

Both actually work "on the server"... But smart usage of each? That's what makes your work look clean, fast, and secure.

A Real-World Analogy: Restaurant Kitchen 🍳

Approach	Analogy
API Route	Like an order-taking employee. You give them the order, they go to the kitchen, verify, and bring back the response after a while...
Server Action	You're talking directly to the chef. You order, they execute immediately, everything happens in the moment without a middleman.

The Core Difference

API Routes

// app/api/posts/route.ts
export async function POST(request: Request) {
  const data = await request.json();
  
  // Validate, process, save to DB
  const post = await db.posts.create({ data });
  
  return Response.json(post);
}

Characteristics:

📁 Write files in /api/*, each file is an endpoint
🔄 Receives request from client, runs on server, returns JSON
⚠️ Exposed and needs extra protection (CSRF, rate limiting)
🌐 Network round-trip between client and server
🔧 Focus: Flexibility, clear separation of concerns

Server Actions

// app/actions.ts
'use server'

export async function createPost(formData: FormData) {
  const title = formData.get('title');
  
  // Direct DB access, no endpoint needed
  const post = await db.posts.create({ 
    data: { title } 
  });
  
  revalidatePath('/posts');
  return post;
}

Characteristics:

🎯 Functions inside Server Components
🚀 Call directly from UI without fetch or JSON
🔒 No visible API endpoint = higher security
⚡ Higher performance (no network round-trip)
🍪 Direct access to cookies, headers, session, DB

Side-by-Side Comparison

Feature	API Routes	Server Actions
Location	`/api/*` folder	Any server file
Call Method	`fetch()`	Direct function call
Response	JSON	Any value
Security	Needs CSRF protection	Built-in security
Performance	Network round-trip	Direct execution
External Access	✅ Yes	❌ No
Best For	Webhooks, external APIs	Mutations, forms

When to Use Each?

✅ Use Server Actions When:

Working with App Router (Next.js 13+)
Doing Mutations (create, update, delete)
Form submissions directly from UI
Performance matters (no round-trip)
Security is priority (no exposed endpoint)

✅ Use API Routes When:

External webhooks (Stripe, GitHub, etc.)
Mobile app backend needs endpoints
Third-party integrations sending requests
Legacy projects without Server Actions
Complex debugging needs clear endpoints

Practical Examples

Example 1: Form Submission → Server Action ✅

// app/actions.ts
'use server'

export async function registerUser(formData: FormData) {
  const email = formData.get('email') as string;
  const password = formData.get('password') as string;
  
  // Validate
  if (!email || !password) {
    return { error: 'Missing fields' };
  }
  
  // Create user
  const user = await db.users.create({
    data: { email, password: await hash(password) }
  });
  
  return { success: true, user };
}

// app/register/page.tsx
import { registerUser } from './actions';

export default function RegisterPage() {
  return (
    <form action={registerUser}>
      <input name="email" type="email" required />
      <input name="password" type="password" required />
      <button type="submit">Register</button>
    </form>
  );
}

Example 2: Stripe Webhook → API Route ✅

// app/api/webhooks/stripe/route.ts
import { headers } from 'next/headers';
import Stripe from 'stripe';

export async function POST(request: Request) {
  const body = await request.text();
  const signature = headers().get('stripe-signature')!;
  
  const event = stripe.webhooks.constructEvent(
    body,
    signature,
    process.env.STRIPE_WEBHOOK_SECRET!
  );
  
  switch (event.type) {
    case 'payment_intent.succeeded':
      await handlePaymentSuccess(event.data.object);
      break;
  }
  
  return Response.json({ received: true });
}

Quick Decision Guide

Use Case	Choice
📝 User registration form	Server Action
🗑️ Delete post from dashboard	Server Action
💬 Add comment	Server Action
💳 Stripe webhook	API Route
📱 Mobile app endpoint	API Route
🔄 GitHub webhook	API Route
❤️ Like/unlike button	Server Action
📤 File upload	Either (depends)

Important Notes

🔒 Security

Server Actions are safer from CSRF attacks because there's no exposed endpoint. But always validate and authenticate inside your functions:

'use server'

export async function deletePost(postId: string) {
  const session = await getSession();
  
  if (!session) {
    throw new Error('Unauthorized');
  }
  
  // Check ownership
  const post = await db.posts.findUnique({ where: { id: postId } });
  
  if (post.authorId !== session.userId) {
    throw new Error('Forbidden');
  }
  
  await db.posts.delete({ where: { id: postId } });
}

📊 Data Fetching

Server Actions are NOT primarily for data fetching — they're for mutations. Data fetching belongs to:

Server Components (direct DB/API calls)
React Query / SWR (client-side)

⚡ Performance

Server Actions are faster because they skip the full HTTP request-response cycle. The function runs directly on the server and returns the result.

Start understanding the UI... and the backend that powers it.

Interfaces you love, code you understand. 💡