Next.js Route Handlers vs Server Actions

Next.js provides two main ways to execute server-side logic and handle data mutations from the client: Route Handlers (API routes) and Server Actions.

While both run on the server, they serve different architectural needs. Knowing when to use each is a common question in frontend interviews.

1. What are Route Handlers?#

Route Handlers are custom request handlers that allow you to build REST-like API endpoints. They are defined in route.ts (or route.js) files and are accessed via standard HTTP requests (GET, POST, PUT, DELETE).

Code Example:#

import { NextResponse } from "next/server";

export async function POST(request: Request) {
  const data = await request.json();
  const newUser = await db.user.create({ data });
  
  return NextResponse.json({ success: true, user: newUser }, { status: 201 });
}

Best Used For:#

• Public APIs: When third-party apps or services need to access your data.
• Webhooks: Handling callbacks from services like Stripe, GitHub, or SendGrid.
• Mobile Clients: If you have a separate mobile app that needs standard JSON endpoints.
• Resource Streaming: Returning custom file downloads, PDF generation, or image assets.

2. What are Server Actions?#

Server Actions are asynchronous functions declared with the "use server" directive. They allow client components to invoke server-side database code directly, behaving like a Remote Procedure Call (RPC). You do not write fetch API requests or declare custom route endpoints.

Code Example:#

"use server";

import { revalidatePath } from "next/cache";

export async function createUserAction(formData: FormData) {
  const email = formData.get("email") as string;
  await db.user.create({ data: { email } });
  
  // Revalidate the cache to show updated data instantly
  revalidatePath("/users");
}

You can import and trigger this function directly inside a client button or HTML form:

import { createUserAction } from "../actions";

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

Best Used For:#

• Form Submissions: Standard application mutations (creating, updating, deleting database items).
• Next.js Internal Cache Mutations: Actions integrate deeply with revalidatePath and revalidateTag to update Next.js page caches dynamically.
• Quick UI Mutations: Small user updates like toggling a "like" button or updating settings.

Comparison Summary#

Key Takeaways#

• Route Handlers act as standard REST API endpoints. Use them when you need to serve public clients, webhooks, or mobile apps.
• Server Actions are internal RPC functions. Use them inside your Next.js application for forms, buttons, and state mutations.
• Server Actions simplify development by removing the need to write API endpoints and fetch client requests for basic database edits.
• Do not use Server Actions if third-party external applications need access to the endpoint; write a Route Handler instead.