Next.js Client and Server Components: Your Guide to Clarity.

In this blog, you'll gain clarity on the often-confusing topic of client and server components in Next.js. We'll break down the differences, explain what each can and can't do, and show you where and how to use them in your projects. Whether you're just starting out or feeling stuck, this guide will help you confidently move forward with your Next.js development, ensuring you're equipped to build both the front and back ends of your applications efficiently.

Client Components:

• Rendered in the browser (Client-Side Rendering, or CSR).
• They can be interactive, handle user input (e.g., forms, buttons), and use browser APIs (like localStorage, window, document).
• They are hydrated (downloaded) to the client and run in the user’s browser after the initial page load.

Server components:

• Rendered on the server (Server-Side Rendering, or SSR).
• They are faster for initial page loads since the HTML is generated on the server and sent to the browser.
• They cannot handle interactions, browser-specific APIs (e.g., window, document), or use client-side hooks like useState, useEffect.
• They are more suitable for static or pre-rendered content and data fetching.‎

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What Can Be Done in Client and Server Components

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Client Components:

• Can manage state using hooks like useState, useEffect, useReducer.
• Can handle user interaction: forms, buttons, event listeners.
• Can access browser APIs: window, document, localStorage, etc.
• Can interact with external APIs from the client-side (e.g., using fetch or axios to call an API).
• Can trigger re-renders based on user actions.

Server component

• Can perform server-side data fetching before sending the HTML to the browser.
• Can fetch data from databases or external APIs on the server.
• Can handle complex pre-rendering tasks (SSR, SSG).
• Cannot manage state or handle browser-based interactivity.
• Cannot directly access browser APIs like window or document.

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Client and Server Component Example.

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Client component
To make a component run on the client, you must use the "use client" directive at the top of the component file.

// ClientComponent.js

"use client"; // This makes the component a Client Component

import { useState } from 'react';

export default function ClientComponent() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

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Server component
Server components do not need the "use client" directive. By default, they are server-side components.

// components/ServerComponent.js

export default async function ServerComponent() {
  const data = await fetch('https://api.example.com/data');
  const result = await data.json();

  return (
    <div>
      <h1>Server-rendered Data:</h1>
      <p>{result.someValue}</p>
    </div>
  );
}

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Where to Use Client and Server Components

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Client Components:

• Interactive elements: If your component requires user interaction (like buttons, forms, modals, etc.), it must be a client component.
• State management: If the component needs to track local state (useState, useEffect), such as handling form input, toggling UI elements, or fetching data on user action, it should be a client component.
• Browser APIs: Any use of browser-specific functionality (like window, localStorage, or document) must be in a client component.

Server Components:

• Static or data-driven content: If a component fetches data and renders it without needing interaction (e.g., fetching product details from an API or database), it can be a server component.
• Content pre-rendering: For content that should be delivered already rendered to the browser to improve performance (such as blog posts, product pages, etc.).
• Avoiding large JavaScript bundles: Since server components don’t need hydration on the client, using them can reduce the amount of JavaScript that gets sent to the browser.

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Where to avoid using:

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Client Components:

• Avoid putting unnecessary logic or data-fetching in client components that could be done on the server. This will reduce the bundle size and improve page load speed.

Server Components:

• Avoid using server components for interactive content (e.g., buttons, form inputs, modals) or anything that requires state management, as server components can’t manage local state or handle client-side interaction.

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‎ For more detailed insights and a deeper understanding, visit these links
server compoents
client components

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