React vs. ReactDOM: Key Differences Every Developer Should Know

• By suggestron
• May 18, 2025May 18, 2025
• With 0 comments

React is one of the most popular JavaScript libraries for building dynamic and interactive user interfaces. Its component-based architecture, virtual DOM, and declarative syntax have made it a go-to choice for front-end developers. However, beginners often get confused between React and ReactDOM—two core packages that work together but serve different purposes.

React has emerged as a dominant force, revolutionising the way developers build interactive user interfaces. Originally developed by Facebook (now Meta), React is now widely adopted by tech giants and startups alike. From high-performance enterprise dashboards to sleek mobile-first websites, React powers a significant portion of the modern web.

But as you begin your journey with React, you’ll quickly encounter another key player in the ecosystem: ReactDOM.

And that’s where confusion often begins.

If you’re just starting out, you may have found yourself asking:

• What exactly is ReactDOM, and how is it different from React?
• Why are there two different libraries — react and react-dom — and what does each one do?
• Can I build apps with React alone, or do I always need ReactDOM?

These are not silly questions — in fact, they reflect a fundamental misunderstanding that many new developers face. It’s easy to overlook the subtle, yet important, distinction between React (the library used to build UI components) and ReactDOM (the tool that renders those components into the browser’s DOM).

The similarity in their names doesn’t help either. It’s natural to assume they’re interchangeable or that one is just a part of the other. However, understanding the difference is critical to mastering React development, improving performance, and ensuring your applications scale efficiently.

This blog post aims to eliminate that confusion once and for all.

We’ll explore:

• The unique role React plays in building user interfaces
• What ReactDOM does behind the scenes to bring your UI to life in a browser
• Why they are maintained as separate packages
• And how knowing the difference helps you write cleaner, more effective code

By the end, you’ll clearly understand what React and ReactDOM are, how they interact, and why both are essential in a modern React project.

Let’s begin by understanding why React is so popular — and what it actually does.

What is React?

React is an open-source JavaScript library for building user interfaces, particularly for single-page applications where seamless user experience and performance are crucial. It was developed and is actively maintained by Meta (formerly Facebook), and it powers some of the world’s most complex web platforms, including Facebook, Instagram, and WhatsApp Web.

At its core, React allows developers to design rich, interactive UIs using a component-based architecture. Instead of working with large monolithic pages, developers build small, reusable components — each encapsulating its own structure, logic, and state.

Core Focus of React

React isn’t a full-fledged framework like Angular. Instead, it focuses on just the view layer of an application (in the MVC pattern). This makes React lightweight, flexible, and easy to integrate into any project.

React helps you:

• Create reusable UI components that manage their own state.
• Build complex user interfaces using simple functions and hooks.
• Structure your application’s UI logically and modularly.

Virtual DOM: Speed and Efficiency

One of React’s most powerful innovations is the Virtual DOM.

The Virtual DOM is an in-memory representation of the real DOM. When a component’s state or props change, React compares the new virtual DOM with the previous one and calculates the most efficient way to update the actual browser DOM — a process known as reconciliation.

This drastically improves performance, especially for applications with frequent UI updates.

Component-Based Architecture

Instead of manipulating HTML and JavaScript separately, React encourages a declarative programming style where components describe what the UI should look like in different states.

Each React component is:

• Self-contained
• Reusable
• Composable — you can nest components inside one another
• Controlled via props (external inputs) and state (internal data)

Examples of React in Action

Here are two ways to create elements in React:

Using React.createElement() (the low-level API):

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const element = React.createElement(‘h1’, null, ‘Hello, world!’);

Using JSX (the preferred, readable syntax):

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const element = <h1>Hello, world!</h1>;

JSX is a syntax extension that looks like HTML but compiles down to React.createElement() calls. It allows developers to write components in a way that closely mirrors the final UI, improving readability and maintainability.

Summary

Feature	Description
Library Name	react
Maintained by	Meta (Facebook)
Core Purpose	Build UI components and manage UI logic
Key Concepts	JSX, Virtual DOM, Components, State, Props
Platform Support	Web, mobile (React Native), desktop, and more

React provides the brains behind your user interface — the architecture, logic, and component structure — but it doesn’t render anything to the screen by itself. For that, we need a renderer like ReactDOM.

 

What is ReactDOM?

As you begin building applications with React, you’ll often hear developers talk about ReactDOM in the same breath as React. It’s even common to see them imported together in entry-point files. But while they are closely related, ReactDOM serves a very different and specific purpose in the React ecosystem.

Definition: ReactDOM is the Library That Connects React to the Actual DOM

ReactDOM is a standalone JavaScript library that’s responsible for interacting directly with the browser’s Document Object Model (DOM) — the tree-like structure that defines the contents and structure of a webpage.

In simple terms, ReactDOM is the rendering engine for web platforms. While React lets you define what the user interface (UI) should look like in terms of components and logic, ReactDOM is the part that takes those components and displays them on the web page.

ReactDOM is included in a separate package called react-dom, and it needs to be imported explicitly in any file where you intend to render React components into the browser.

ReactDOM: The Bridge Between React and the Browser

Think of ReactDOM as the bridge that connects your component-based React code to the actual HTML elements in the browser. Without ReactDOM, your React components would simply be JavaScript objects floating in memory—they wouldn’t appear on the screen.

ReactDOM enables this bridge by:

• Creating a root in the DOM where your React application will live
• Rendering the component tree into that root element
• Updating the DOM efficiently whenever your app’s state changes
• Cleaning up by unmounting components when they’re no longer needed

This means ReactDOM is the piece of the puzzle that takes all the logic and structure created with React and turns it into visible, interactive content in the browser.

What Does ReactDOM Actually Do?

Let’s break down the main tasks performed by ReactDOM in more detail:

✅ Mounting the App

ReactDOM inserts your entire React application into a specific part of the HTML document—typically a <div> with an ID like root. This mounting process is the first step in displaying your React app to users.

✅ Rendering Components

After mounting the app, ReactDOM continuously listens for changes in your components’ state or props. When something changes, it uses React’s Virtual DOM algorithm to update only the parts of the actual DOM that need to change—this makes React apps incredibly fast and efficient.

✅ Hydrating Server-Rendered Content

In server-side rendering (SSR), HTML content is first rendered on the server and sent to the browser. ReactDOM then “hydrates” this static content, turning it into a fully interactive React app. This allows for faster initial page loads and better SEO.

✅ Unmounting Components

When a component is no longer needed—for example, if a user navigates away from a section—ReactDOM can remove it from the DOM to free up memory and improve performance.

Essential Methods Provided by ReactDOM

ReactDOM provides a handful of powerful methods that developers use to manage rendering. Here are the most important ones:

ReactDOM.createRoot()

Introduced in React 18, this method is used to create a root for rendering in the new concurrent mode, which allows React to interrupt rendering tasks for better performance.

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const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(<App />);

This is now the recommended way to start rendering React applications.

ReactDOM.render()

This was the traditional method for rendering components prior to React 18. It looks like this:

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ReactDOM.render(<App />, document.getElementById(‘root’));

While still supported in older apps, it’s considered legacy and should be avoided in new React projects.

ReactDOM.hydrate()

This method is used when you want to hydrate (i.e., activate) HTML that was rendered on the server. It allows for seamless server-to-client rendering transitions.

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ReactDOM.hydrate(<App />, document.getElementById(‘root’));

ReactDOM.unmountComponentAtNode()

This method removes a React component from the DOM and cleans up its associated resources.

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ReactDOM.unmountComponentAtNode(document.getElementById(‘root’));

Useful when dynamically rendering or replacing content in a single-page app.

Why ReactDOM Exists Separately from React

You might wonder why ReactDOM wasn’t just bundled into React itself. The answer lies in flexibility and modularity.

React was designed to be platform-agnostic. That means the same React code can theoretically run in:

• A web browser (via ReactDOM)
• A mobile device (via React Native)
• A terminal window (via Ink)
• A 3D WebGL canvas (via React Three Fiber)

By separating the platform-specific rendering logic into libraries like react-dom, React stays lightweight and adaptable to different environments. This separation also allows for the independent development and optimization of rendering engines based on the platform’s specific needs.

Quick Comparison Table: React vs ReactDOM

To fully understand the distinction between React and ReactDOM, it helps to compare them side by side. While they are often used together, each plays a fundamentally different role in a React application.

Below is a detailed comparison table to help you quickly grasp how they differ across various aspects:

Feature	React	ReactDOM
Purpose	Building and managing UI components.	Rendering UI components to the DOM.
Package	react	react-dom
Virtual or Real DOM	Works with the Virtual DOM (a lightweight copy of the actual DOM).	Works with the Real DOM (the actual web page structure in the browser).
Core Functions	createElement, JSX, Hooks like useState, useEffect, etc.	render, hydrate, createPortal, unmountComponentAtNode.
Common Usage	Writing UI logic, creating components, managing state and props.	Mounting components into the browser’s HTML document.
Example Method	React.createElement()	ReactDOM.render() or ReactDOM.createRoot().render() (React 18+)

 

 

Why React and ReactDOM are Separated?

One of the most important architectural decisions in the React ecosystem is the separation between React and ReactDOM. This may seem confusing at first—after all, they often work together—but this split is intentional and rooted in a powerful software design principle called separation of concerns.

Separation of Concerns: Keeping Logic and Rendering Apart

React is responsible for building and managing UI components—it focuses entirely on how your application should look and behave based on its current state. This includes handling component logic, data flow, and user interaction via hooks and props.

On the other hand, ReactDOM handles the rendering of those components into the web browser. It connects the abstract component tree you create with the actual Document Object Model (DOM) in your HTML file.

By separating these responsibilities, React achieves:

• Modularity: Each part of the system focuses on one job.
• Reusability: The same React components can be rendered on multiple platforms.
• Flexibility: You can plug React into any rendering environment—web, mobile, 3D, and more.

React Is Platform-Agnostic

Unlike traditional UI libraries tied to the browser, React was designed from the ground up to be platform-independent. This means that while it was originally introduced for building web apps, it has since expanded to support other platforms as well.

React doesn’t directly manipulate the DOM. Instead, it uses a Virtual DOM to compute the best way to update the UI. That “diffed” information then gets passed to the renderer—like ReactDOM for the browser—to make the final changes.

ReactDOM Is the Web Renderer

ReactDOM is just one of many possible renderers for React. It is specifically designed to render React components into web browsers, handling tasks such as:

• Mounting components into HTML elements
• Updating the DOM efficiently
• Hydrating server-rendered pages
• Unmounting components when necessary

It serves as the bridge between React’s component logic and the browser’s real DOM.

Other Renderers Beyond ReactDOM

One of the major advantages of this architectural separation is that React can be reused across different environments by simply swapping out the rendering engine. Here are some of the most popular alternatives to ReactDOM:

Renderer	Platform	Description
ReactDOM	Web browsers	Renders components into the browser’s HTML DOM.
React Native	iOS and Android apps	Uses native mobile components instead of HTML and CSS.
React Native Web	Web browsers (from React Native code)	Allows React Native components to render on the web.
React Three Fiber	3D WebGL scenes	Renders 3D content using Three.js, powered by React components.
Ink	Command-line interface (CLI)	Renders React components into interactive terminal UIs.

This flexibility means your component logic—your state management, event handling, and structure—can remain the same, even as the output medium changes entirely.

The Big Picture

By separating React and ReactDOM, the React ecosystem remains:

• Scalable across platforms
• Maintainable with cleaner code separation
• Future-proof, as new rendering engines can be developed without rewriting the core logic

This decision has allowed React to move far beyond just the browser—and has helped it become the most versatile and widely adopted UI library in the JavaScript world.

 

ReactDOM Methods Explained with Examples

As the official rendering library for React on the web, ReactDOM provides several key methods that enable React components to interact with the actual DOM. These methods are used to render, hydrate, unmount, or even port components to places outside the main root element.

Each method serves a specific purpose depending on the stage and style of rendering in your React application. Let’s break them down one by one with simple examples.

1. ReactDOM.render() – The Legacy Approach (Pre-React 18)

Purpose:

Used to render a React component into a DOM node. This was the standard method prior to React 18.

✅ Example:

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import React from ‘react’;

import ReactDOM from ‘react-dom’;

import App from ‘./App’;

 

ReactDOM.render(<App />, document.getElementById(‘root’));

⚠️ Important Notes:

• Deprecated in React 18 and replaced by createRoot().
• Still used in older projects for backward compatibility.
• Doesn’t support concurrent features like streaming or transitions.

2. ReactDOM.createRoot() – The Modern Approach (React 18+)

Purpose:

Introduced in React 18, this method enables Concurrent Mode, unlocking new features like automatic batching, streaming rendering, and more responsive user interfaces.

✅ Example:

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import React from ‘react’;

import ReactDOM from ‘react-dom/client’;

import App from ‘./App’;

 

const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(<App />);

✅ Benefits:

• Improved performance with concurrent rendering
• Built-in support for React 18 features
• Replaces ReactDOM.render() for modern apps

3. ReactDOM.hydrate() – For Server-Side Rendering (SSR)

Purpose:

Used to hydrate (attach event listeners to) server-rendered HTML sent to the client. It turns static HTML into a fully interactive React app.

This is crucial in SSR apps where the initial content is rendered on the server for performance and SEO, and React takes over on the client side.

✅ Example:

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import React from ‘react’;

import ReactDOM from ‘react-dom’;

import App from ‘./App’;

 

ReactDOM.hydrate(<App />, document.getElementById(‘root’));

When to Use:

• In frameworks like Next.js, Remix, or custom SSR setups.
• For improved initial load speed and SEO.

4. ReactDOM.unmountComponentAtNode() – Removing Components’

Purpose:

Unmounts a React component from a specified DOM node, cleans up memory, and detaches event listeners.

Example:

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ReactDOM.unmountComponentAtNode(document.getElementById(‘modal’));

Use Cases:

• Removing components that were rendered dynamically
• Cleaning up modal or popup components
• Ensuring no memory leaks in single-page apps

5. ReactDOM.createPortal() – Rendering Outside the Root DOM

Purpose:

Used to render a child component into a different part of the DOM tree than the main app root. This is especially useful for modals, tooltips, or overlays that should not be confined by parent components’ styling or hierarchy.

Example:

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import ReactDOM from ‘react-dom’;

 

function Modal({ children }) {

return ReactDOM.createPortal(

children,

document.getElementById(‘modal-root’)

);

}

Here, the modal is rendered into a DOM element with id=”modal-root”, outside the main app container.

Benefits:

• Maintains visual layering (z-index) correctly
• Avoids style inheritance issues
• Works well with accessibility requirements

Summary Table: ReactDOM Methods at a Glance

Method	Purpose	React Version	Key Use
render()	Mounts a React component	Pre-React 18	Traditional rendering
createRoot()	Enables concurrent rendering	React 18+	Modern, recommended approach
hydrate()	Attaches React to SSR HTML	All versions	Server-side rendering
unmountComponentAtNode()	Removes a component from the DOM	All versions	Cleanup and memory management
createPortal()	Renders component outside the main root	All versions	Modals, tooltips, overlays

 

 

Practical Code Examples

To solidify your understanding of how React and ReactDOM work together, let’s look at two practical code examples. These will demonstrate exactly how components are built in React and how they are rendered to the actual browser DOM using ReactDOM.

Example 1: Using React and ReactDOM in a Basic App

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import React from ‘react’;

import ReactDOM from ‘react-dom/client’;

 

function App() {

return <h1>Hello, world!</h1>;

}

 

const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(<App />);

How This Works

Step 1: React Defines the Component

In the line:

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function App() {

return <h1>Hello, world!</h1>;

}

You’re defining a functional React component named App. This component simply returns a JSX element—a heading with the text “Hello, world!”.

JSX is a syntax extension that looks like HTML but gets transpiled by Babel into a JavaScript call like:

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React.createElement(‘h1’, null, ‘Hello, world!’)

This element is not yet visible in the browser. It’s just a virtual representation of what you want the UI to look like.

Step 2: ReactDOM Renders It to the Browser

The following lines are where the rendering takes place:

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const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(<App />);

Here’s what happens:

• document.getElementById(‘root’) selects a DOM node from your HTML file, typically something like <div id=”root”></div>.
• ReactDOM.createRoot() tells ReactDOM to initialize a rendering root in that DOM element.
• root.render(<App />) tells ReactDOM to take the App component, interpret its virtual DOM, and render it into the real DOM inside the #root element.

So while React builds the virtual representation of your UI, ReactDOM makes it visible by inserting the appropriate HTML into the browser.

Example 2: Using React.createElement() Directly

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React.createElement(‘div’, null, ‘Hello from React’)

What This Does

This line is the pure JavaScript version of JSX, and it’s what JSX gets compiled into under the hood.

Here’s a breakdown of the syntax:

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React.createElement(

type,     // ‘div’ – the HTML tag to create

props,    // null – no attributes or event handlers

children  // ‘Hello from React’ – the text content inside the <div>

);

This call creates a virtual DOM element representing:

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<div>Hello from React</div>

While this code defines a React element, it won’t display anything unless it’s passed to a renderer like ReactDOM.render() or root.render().

Example with Rendering:

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import React from ‘react’;

import ReactDOM from ‘react-dom/client’;

 

const element = React.createElement(‘div’, null, ‘Hello from React’);

const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(element);

This snippet shows how you can use React.createElement() manually and still render it using ReactDOM.

When Should You Use createElement()?

• Typically used internally by React after transpiling JSX.
• Useful in custom renderers or dynamic component generation.
• In most cases, developers prefer JSX for better readability and cleaner code.

 

Common Mistakes Developers Make

As developers learn React, especially those coming from HTML/CSS/JavaScript backgrounds, it’s easy to blur the lines between React and ReactDOM. While they work closely together, they are fundamentally different libraries with unique responsibilities.

Here are some of the most common mistakes developers make when working with React and ReactDOM — and how to avoid them.

❌ 1. Confusing React and ReactDOM Usage

Many beginners mistakenly believe that ReactDOM is interchangeable with React or is part of the core react package. This misunderstanding leads to using the wrong import statements or assuming that both libraries do the same thing.

Mistake:

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// Incorrect assumption: Everything comes from ‘react’

import { render, useState } from ‘react’;

✅ Correct Approach:

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import React, { useState } from ‘react’;

import ReactDOM from ‘react-dom/client’;

Explanation:

• useState is a React hook that belongs to the react package.
• render() or createRoot() comes from react-dom, which handles rendering to the browser.

Solution: Understand that:

• react is for building components and handling logic
• react-dom is for rendering those components to the web

❌ 2. Using ReactDOM.render() in React 18+ Projects

One of the biggest breaking changes introduced in React 18 is the shift from ReactDOM.render() to ReactDOM.createRoot(). Continuing to use the old method will cause deprecation warnings and missed opportunities to use concurrent features like streaming and automatic batching.

Old (React 17 and below):

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ReactDOM.render(<App />, document.getElementById(‘root’));

✅ New (React 18+):

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const root = ReactDOM.createRoot(document.getElementById(‘root’));

root.render(<App />);

Solution:
Always use createRoot() in React 18+ to future-proof your code and gain access to performance enhancements and features designed for concurrent rendering.

❌ 3. Ignoring ReactDOM-Specific Methods

Many developers focus solely on React and overlook powerful methods provided by ReactDOM, such as createPortal, hydrate, and unmountComponentAtNode. These tools can solve specific rendering problems but are often underused due to lack of awareness.

Example:

• Using a modal component and forcing it into the component tree when ReactDOM.createPortal() is the better solution.

✅ Use Case:

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ReactDOM.createPortal(<Modal />, document.getElementById(‘modal-root’));

Solution:
Familiarize yourself with ReactDOM’s extended capabilities. These methods help you build more flexible, high-performance UIs — especially for things like:

• Modals and overlays (via createPortal)
• SSR hydration (hydrate)
• Dynamic cleanup (unmountComponentAtNode)

❌ 4. Assuming React Can Work Without ReactDOM in Web Apps

Some developers mistakenly believe that simply writing components with React is enough for a functional web app. However, in a web environment, React requires a renderer to interact with the DOM — and that’s exactly what ReactDOM provides.

Misconception:

“React alone can render my UI in the browser.”

✅ Reality:

React defines the UI logic, but ReactDOM is needed to render it into the webpage’s HTML structure.

Solution:
In web applications, always include react-dom alongside react. Without it, your app has no way of connecting to the actual DOM.

Best Practices for Using React and ReactDOM

To make the most out of your React development experience—and to write clean, maintainable, and performant applications—it’s essential to follow a few best practices when working with React and ReactDOM. These practices help you avoid common pitfalls, prepare your codebase for future updates, and make debugging far easier.

Let’s look at some of the most recommended strategies when using these two powerful libraries together.

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✅ 1. Use createRoot() in React 18+ for Concurrent Features

With the release of React 18, ReactDOM.createRoot() replaced ReactDOM.render() as the preferred method for rendering applications to the DOM. This change isn’t just syntactic—it introduces a new rendering architecture called Concurrent Mode, which allows React to pause and resume rendering for better responsiveness and efficiency.

Why This Matters:

Using createRoot() ensures:

• Automatic batching of state updates

• Support for transitions and streaming server rendering

• Future compatibility with upcoming React features

✅ Example:

Best Practice:

Always use createRoot() when starting a new project with React 18 or above.

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✅ 2. Clearly Organize Imports: react vs react-dom

One of the simplest ways to maintain code clarity is to separate your concerns at the import level. React and ReactDOM come from different packages and serve different purposes, so you should reflect that in your code organization.

Why This Matters:

• Prevents mixing logic and rendering concerns

• Helps you instantly identify where each method comes from

• Avoids mistakenly calling DOM-related functions from the wrong package

✅ Example:

Avoid doing this:

Best Practice:

Use React for logic and hooks, and ReactDOM only for rendering-related methods in your entry files (index.js, main.jsx, etc.).

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✅ 3. Understand the Separation for Better Debugging and Maintenance

When things go wrong—such as components not updating, improper rendering, or performance bottlenecks—it’s important to know which part of your stack is responsible.

Understanding the division between React (UI logic) and ReactDOM (rendering) helps you:

• Quickly isolate issues (e.g., a component not showing up might be a rendering issue, not a state issue)

• Write more modular and testable code

• Make your app platform-agnostic (e.g., reuse logic between web and mobile via React Native)

Example Scenarios:

• If your state updates but the UI doesn’t reflect the change, the issue might be with how ReactDOM is rendering (or not rendering) the component.

• If the layout looks wrong in a modal or overlay, check if you need to use ReactDOM.createPortal().

Best Practice:

Mentally (and structurally) separate UI logic (React) from DOM interaction (ReactDOM). This not only aligns with React’s design philosophy but also makes your app easier to scale, test, and debug.

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✨ Bonus Tip: Keep ReactDOM Usage Minimal and Isolated

In most projects, ReactDOM is only needed once—typically in the file where the root of your application is rendered (like index.js). Keep all ReactDOM-related logic isolated there. The rest of your app should be focused on component logic using React.

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Frequently Asked Questions (FAQs)

Q1. Is ReactDOM part of React?

Answer:
No, ReactDOM is not part of React itself. It is a separate package (react-dom) that is specifically responsible for rendering React components into the web browser’s DOM. While React defines the structure and logic of your UI, ReactDOM is the tool that turns those definitions into visible HTML on the page.

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Q2. Can React work without ReactDOM?

Answer:
React requires a renderer to function properly. On the web, that renderer is ReactDOM. However, React is designed to be platform-agnostic, so it can work with other renderers too. For example, React Native is used to render components to mobile devices. So while React can work without ReactDOM, you always need a platform-specific renderer to display the UI.

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Q3. What replaced ReactDOM.render() in React 18?

Answer:
In React 18, the traditional ReactDOM.render() method was replaced by ReactDOM.createRoot(). This new API enables concurrent rendering features, such as automatic batching, streaming rendering, and improved performance for modern apps. The correct pattern now is:

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Q4. What is the use of ReactDOM.createPortal()?

Answer:
ReactDOM.createPortal() is used to render a component outside of the main DOM hierarchy. This is especially useful for modals, popups, tooltips, and overlays, where you want the component to exist in a different part of the DOM (usually at the root level) while maintaining React’s component tree relationships and state.

✅ Example Use Case:

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