Guide to build a modern Web App using Next.js 14 (App Router), Fully authentication (NextAuth), Theming and i18n

Introduction to Next.js and Its Dominance

In the last few years, Next.js has got an enormous attention in web development fields, especially with the growing of React usage worldwide. Its simplicity, power, and flexibility make it the favorite choice for most developers who would want to build scalable and performant applications. Next.js developed by Vercel, it offers a framework with routing, server-side rendering, static site generation and API routes.

🌟 Why to use Next.js?
Next.js is impressive for certain reasons:

1. Server-Side Rendering (SSR): Which is often considered one of the main strengths of Next.js (it has native support for SSR), which enhance the performance and SEO because pages are rendered on the server instead of by the client.

2. Static Site Generation (SSG): In Next.js, developers can generate static pages at build time; this increases page loading a lot and reduces the demand on the server.

3. Hybrid Model: By using Next.js we will have all of Server-Side Rendering (SSR), Static Site Generation (SSG), and Client-Side Rendering (CSR) within the same framework. Thus, it allows developers to be flexible with how they fetch and display data.

4. API Routes: Next.js lets you build API routes directly in your app, making it easy to handle any kind of backend functionality without the need to have a separate traditional backend.

5. In addition, Vercel which is the creator of Next.js provides an optimized deployment platform for Next.js, enabling instant deployments with features like automatic scaling, zero-config setups, and serverless functions.

🌟 Why to use App Router?
With the advantage of Next.js 13, the "App Router" became the preferred way of routing and replaced the existing "pages routing system" because of the following factors:

• Layouts: One of the most advanced features of App Router. Which allows you (As the name suggests) to define multiple reusable layout level inside an application to keep a consistent structure among many routes or pages.
• Loading UI: which supports the display of spinners or skeleton screens while data fetching for a particular page or component.
• Colocation of Data and UI: Which help in collocating UI components with the data they depend on.
• React Server Components: Taking advantage of the powerful React 19 Server Components, App Router will make sure that load time is faster due to the smaller JavaScript bundle being downloaded to the client.

All previous factors make App Router more efficient, maintainable, and scalable.

Apply Authentication using NextAuth
NextAuth.js provides a very straightforward way to apply powerful authentication in your Web App. It supports providers like Google, GitHub, and even allows self-made email/password solutions.

🌟 Why NextAuth.js?

• Ease of Integration: NextAuth.js works well with Next.js, so you are allowed to build authentications with a minimum of configuration.
• Secure Defaults: Secure defaults are things like HTTP-only cookies, CSRF protection, and encryption for session tokens.
• OAuth Providers: Easily add flexible OAuth providers like Google, Facebook, or GitHub, custom username/password logins …
• Serverless Compatibility: It's designed to work with Next.js API routes. Which is ideal for modern stateless architectures.

🌟 Styling with Tailwind CSS
Tailwind CSS is a very popular utility-first CSS framework featuring a lot of flexibility and simplicity. It allows developers to create responsive, scalable interfaces without custom CSS, which is why it's perfectly suitable for Next.js apps.

🌟 Why to use Tailwind CSS?

• In Tailwind, developers can implement CSS styles right within HTML or JSX using className props that make it faster to build UI components without having to switch between files.
• Highly Customizable: using Tailwind configuration file which contains options to customize all theme colors, breakpoints, and other design tokens.
• Fully support of responsive design by providing easy way to represent screen dimensions using intuitive for class naming regarding views on mobile, tablet, and desktop.

🌟 Apply multiple theming modes:
Most modern applications give users an opportunity to choose between a light theme and a dark theme. That gives them a personalized experience. Next.js can handle theming quite easily using "next-themes" combined with Tailwind CSS.

🌟 Internationalization (i18n) with Next.js
Global applications may often need to support multiple languages. Next.js provides built-in internationalization support by using "i18next" with some extra customization.

🌟 Practical example

In the following project I have developed a website using Nextjs 14 with App Router, Fully authentication using NextAuth (SignUp, ForgetPassword, ResetPassword), Responsive Web Design using Tailwind CSS, i18n and multiple themes support.

💻💻 [Project on GitHub]: (https://github.com/alaa-m1/nextjs14-approuter-nextauth-shopsfinder)