API routes vs server actions decision in NextJS

Introduction

API routes and server actions both let your Next.js app talk to the server. Choosing the right one helps your app work better and be easier to build.

You want to handle data fetching or updates from the client with a clear API endpoint.

You need to share server logic between different parts of your app easily.

You want to keep server code close to your components for simpler code.

You want to avoid writing extra API endpoints for simple server tasks.

You want to use built-in Next.js features for server communication without extra setup.

Syntax

NextJS

API Route example:
// pages/api/hello.js
export default function handler(req, res) {
  res.status(200).json({ message: 'Hello from API route!' })
}

Server Action example:
'use server'
export async function addData(data) {
  // server logic here
  return 'Data added'
}

API routes live in the pages/api folder and act like normal API endpoints.

Server actions are functions marked with 'use server' and can be called directly from components.

Examples

This API route handles POST requests and returns success.

NextJS

// API route example
export default function handler(req, res) {
  if (req.method === 'POST') {
    res.status(200).json({ success: true })
  } else {
    res.status(405).end()
  }
}

This server action saves a user and returns a confirmation.

NextJS

'use server'
export async function saveUser(user) {
  // save user to database
  return 'User saved'
}

Sample Program

This example shows a server action greet called from a React component. When you click the button, it calls the server action and shows the greeting.

NextJS

// app/actions.js
'use server'
export async function greet(name) {
  return `Hello, ${name}!`
}

// app/page.jsx
'use client'
import { useState } from 'react'
import { greet } from './actions'

export default function Page() {
  const [message, setMessage] = useState('')

  async function handleClick() {
    const result = await greet('Friend')
    setMessage(result)
  }

  return (
    <main>
      <button onClick={handleClick}>Greet</button>
      <p>{message}</p>
    </main>
  )
}

Important Notes

Use API routes when you want a traditional REST or JSON API accessible from anywhere.

Use server actions to keep server logic close to components and simplify data handling.

Server actions require Next.js 14+ and App Router setup.

Summary

API routes create separate API endpoints for client-server communication.

Server actions let you call server code directly from components without extra endpoints.

Choose based on your app's needs: API routes for broad API use, server actions for simpler, integrated server calls.

Practice

1. What is the main difference between Next.js API routes and server actions?

easy

A. API routes and server actions are exactly the same in Next.js.

B. API routes run only on the client; server actions run only on the server.

C. API routes create separate endpoints; server actions call server code directly from components.

D. API routes are used for styling; server actions handle routing.

Solution

1. Step 1: Understand API routes purpose

   API routes create separate API endpoints that the client can call to communicate with the server.

2. Step 2: Understand server actions purpose

   Server actions allow calling server code directly from React components without creating separate endpoints.

3. Final Answer:

   API routes create separate endpoints; server actions call server code directly from components. -> Option C

4. Quick Check:

   API routes vs server actions difference = D [OK]

Hint: API routes = endpoints; server actions = direct calls [OK]

Common Mistakes:

• Thinking API routes run on client side
• Confusing server actions with styling or routing
• Believing API routes and server actions are identical

2. Which of the following is the correct way to define a server action in Next.js?

easy

A. export default function handler(req, res) { /* server code */ }

B. export async function actionName() { /* server code */ }

C. function actionName() { return Server Action }

D. const actionName = () => fetch('/api/data')

Solution

1. Step 1: Identify server action syntax

   Server actions are defined as exported async functions that run on the server.

2. Step 2: Compare with API route syntax

   API routes use a default export function with (req, res) parameters, not named async functions.

3. Final Answer:

   export async function actionName() { /* server code */ } -> Option B

4. Quick Check:

   Server action syntax = B [OK]

Hint: Server actions use named async functions exported directly [OK]

Common Mistakes:

• Using default export with req, res (API route style)
• Writing server actions as React components
• Calling fetch inside server action definition

3. Given this Next.js server action code, what will be the output when called from a component?

export async function addNumbers(a, b) {
  return a + b;
}

medium

A. Returns a Promise resolving to the sum of a and b.

B. Returns undefined because server actions cannot return values.

C. Throws a syntax error due to missing parameters.

D. Returns a string concatenation of a and b.

Solution

1. Step 1: Analyze the server action function

   The function is async and returns the sum of a and b, which is a number.

2. Step 2: Understand async function return

   Async functions return a Promise that resolves to the returned value, here the sum.

3. Final Answer:

   Returns a Promise resolving to the sum of a and b. -> Option A

4. Quick Check:

   Async function returns Promise with sum = A [OK]

Hint: Async server actions return Promises with results [OK]

Common Mistakes:

• Thinking server actions cannot return values
• Confusing number addition with string concatenation
• Assuming syntax error due to parameters

4. You wrote this API route in Next.js but it throws an error:

export async function handler(req, res) {
  res.status(200).json({ message: 'Hello' });
}

What is the error and how to fix it?

medium

A. Response method json is invalid; use send instead.

B. Should use server action syntax instead of API route syntax.

C. Function must not be async in API routes.

D. Missing default export; change to export default async function handler(req, res).

Solution

1. Step 1: Identify API route export requirement

   API routes require a default export function to handle requests.

2. Step 2: Fix export statement

   Change named export to default export: export default async function handler(req, res).

3. Final Answer:

   Missing default export; change to export default async function handler(req, res). -> Option D

4. Quick Check:

   API route default export required = C [OK]

Hint: API routes need default export function [OK]

Common Mistakes:

• Using named export instead of default export
• Confusing API routes with server actions syntax
• Incorrect response method usage

5. You want to build a Next.js app that needs a public API for multiple clients and also some simple server logic tightly integrated with components. Which approach should you choose?

hard

A. Use API routes for the public API and server actions for simple server logic inside components.

B. Use only server actions for everything to keep code simple.

C. Use only API routes for all server logic to avoid confusion.

D. Use client-side fetching only; avoid server code.

Solution

1. Step 1: Analyze app needs

   The app requires a public API accessible by multiple clients and simple server logic integrated with components.

2. Step 2: Match features to approaches

   API routes are best for broad public APIs; server actions are ideal for simple, direct server calls from components.

3. Final Answer:

   Use API routes for the public API and server actions for simple server logic inside components. -> Option A

4. Quick Check:

   Public API + integrated logic = A [OK]

Hint: Public API = API routes; simple logic = server actions [OK]

Common Mistakes:

• Using only server actions for public APIs
• Using only API routes for simple component logic
• Avoiding server code when needed