Why server components are the default in NextJS

Introduction

Server components run on the server by default to make web apps faster and simpler. They send only the needed HTML to the browser, saving time and data.

When you want faster page loads by sending ready HTML from the server.

When you want to keep sensitive data or API keys safe on the server.

When you want to reduce the amount of JavaScript sent to the browser.

When you want simpler code that doesn't need to handle browser events.

When you want to improve SEO by having fully rendered pages on the server.

Syntax

NextJS

export default function MyComponent() {
  return <h1>Hello from Server Component</h1>
}

By default, components in Next.js 13+ are server components unless marked otherwise.

You can make a component a client component by adding 'use client' at the top.

Examples

This is a simple server component that renders a paragraph.

NextJS

export default function ServerComponent() {
  return <p>This runs on the server.</p>
}

This is a client component because it uses state and browser events.

NextJS

'use client'

import { useState } from 'react'

export default function ClientComponent() {
  const [count, setCount] = useState(0)
  return <button onClick={() => setCount(count + 1)}>Count: {count}</button>
}

Sample Program

This component runs on the server by default and sends HTML to the browser.

NextJS

export default function Greeting() {
  return <h2>Welcome to Server Components!</h2>
}

Important Notes

Server components cannot use browser-only APIs like 'window' or 'document'.

They help reduce JavaScript bundle size sent to the client.

Use client components only when you need interactivity like event handlers.

Summary

Server components run on the server by default to improve speed and security.

They send only HTML to the browser, reducing data and load time.

Use client components only when you need browser features like state or events.

Practice

1. Why are server components the default in Next.js?

easy

A. They allow direct access to browser events and state management.

B. They improve speed by running on the server and sending only HTML to the browser.

C. They require less server resources by running on the client.

D. They enable real-time updates without refreshing the page.

Solution

1. Step 1: Understand server component behavior

   Server components run on the server and send only HTML to the browser, reducing data transfer and improving speed.

2. Step 2: Compare with client components

   Client components handle browser events and state, but server components focus on fast, secure rendering.

3. Final Answer:

   They improve speed by running on the server and sending only HTML to the browser. -> Option B

4. Quick Check:

   Server components = faster, secure HTML delivery [OK]

Hint: Server components send HTML, client components handle events [OK]

Common Mistakes:

• Confusing server components with client-side event handling
• Thinking server components run in the browser
• Assuming server components manage state like client components

2. Which of the following is the correct way to mark a component as a client component in Next.js?

easy

A. Use export default clientComponent() syntax.

B. Wrap the component in <ClientComponent> tags.

C. Add the directive use client at the top of the file.

D. Add client: true in the component props.

Solution

1. Step 1: Recall client component syntax

   In Next.js, to mark a component as client-side, you add the directive use client at the very top of the file.

2. Step 2: Eliminate incorrect options

   Wrapping in tags, special export syntax, or props flags are not valid ways to mark client components.

3. Final Answer:

   Add the directive use client at the top of the file. -> Option C

4. Quick Check:

   Client component directive = 'use client' [OK]

Hint: Client components start with 'use client' directive [OK]

Common Mistakes:

• Trying to mark client components with props or wrappers
• Placing 'use client' inside the component body
• Confusing export syntax with client directives

3. Consider this Next.js component code:

export default function Page() {
  return (
    <div>Hello from server component</div>
  )
}

What will the browser receive when this page loads?

medium

A. Plain HTML content: <div>Hello from server component</div>.

B. An error because no client directive is present.

C. A fully interactive React component with event handlers.

D. Empty content because server components do not render.

Solution

1. Step 1: Identify component type

   The component has no 'use client' directive, so it is a server component by default.

2. Step 2: Understand server component output

   Server components render HTML on the server and send plain HTML to the browser without React event handlers.

3. Final Answer:

   Plain HTML content: <div>Hello from server component</div>. -> Option A

4. Quick Check:

   Server component output = plain HTML [OK]

Hint: No 'use client' means server component sends HTML only [OK]

Common Mistakes:

• Expecting React interactivity without 'use client'
• Thinking server components cause errors without client directive
• Assuming server components send JavaScript to browser

4. You have this Next.js component:

export default function Button() {
  const [count, setCount] = React.useState(0);
  return <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>;
}

What is the main problem with this code in Next.js 13+?

medium

A. Buttons cannot have event handlers in Next.js.

B. The useState hook is not imported from React.

C. The arrow function in onClick is invalid syntax.

D. It lacks the use client directive, so state and events won't work.

Solution

1. Step 1: Check component type and hooks usage

   The component uses React state and event handlers, which require client-side execution.

2. Step 2: Identify missing client directive

   Without the 'use client' directive at the top, this component is treated as a server component, so hooks and events won't work.

3. Final Answer:

   It lacks the use client directive, so state and events won't work. -> Option D

4. Quick Check:

   State + events need 'use client' directive [OK]

Hint: State or events require 'use client' directive [OK]

Common Mistakes:

• Forgetting to add 'use client' for interactive components
• Assuming hooks work in server components
• Thinking arrow functions cause syntax errors here

5. You want to build a Next.js page that fetches data securely on the server and shows a button that increments a counter on click. How should you organize your components?

hard

A. Use a server component for data fetching and embed a client component for the button with state.

B. Make the entire page a client component to handle data fetching and button state.

C. Use only server components because client components are slower.

D. Fetch data in the client component and handle button state in the server component.

Solution

1. Step 1: Separate concerns by component type

   Data fetching is best done in server components for security and speed, while interactive UI needs client components.

2. Step 2: Combine server and client components properly

   Use a server component to fetch and render data, then include a client component inside it for the button with state and events.

3. Final Answer:

   Use a server component for data fetching and embed a client component for the button with state. -> Option A

4. Quick Check:

   Server fetch + client interactivity = best practice [OK]

Hint: Fetch on server, interactive parts on client [OK]

Common Mistakes:

• Making entire page client-side losing server benefits
• Trying to fetch data inside client components
• Mixing state logic in server components