What is the difference between the traditional pages directory and the src/app directory in Next.js?

Hey folks! What’s up? Hope everything is good. Today, I’ll discuss the differences between the traditional pages directory and the src/app directory in Next.js. in my previous article, I explained how Next.js projects are different from React.js projects. where I dive deep into next.js and react.js.

The current version of Next.js

The current stable version of Next.js is Next.js 15, which was officially released in late 2024. This version introduced several improvements, including the stabilization of Turbopack, which provides faster development builds. It also offers better optimization for code splitting and caching.

Next.js 15 enhances the predictability of caching and server-side rendering and introduces features like Partial Prerendering (PPR) and new APIs for deferring tasks after a response.

With Next.js 15, developers can expect faster local development workflows, improved support for server components, and a smoother experience when scaling applications. For more detailed insights into these new features, it’s recommended to check the release notes and official documentation.

src/app directory

The src/app directory was introduced in Next.js 13, as part of a major overhaul of the framework. This change aimed to improve the developer experience and offer more flexibility for building applications, particularly with the introduction of features like React Server Components and Concurrent Rendering.

The app directory is an experimental feature in Next.js 13, and it became a central part of the framework in subsequent minor releases. It provides a new way to structure applications, offering features like layouts, nested routes, templates, and server-side rendering out of the box.

With the release of Next.js 13.2 and later versions, the src/app directory was promoted from an experimental feature to a more stable, production-ready feature, although some aspects may still evolve as Next.js continues to improve its API and features.

Key Releases Related to src/app:

• Next.js 13 (October 2022): Introduced the app directory as part of the new app structure, along with support for React Server Components and improved routing capabilities.

• Next.js 13.2+ (2023): The app directory gained more stability and additional features like layouts, templates, and concurrent rendering.

So, if you're working with Next.js 13 or later, you have the option to use the src/app directory to structure your app more flexibly, but it's still essential to follow the Next.js documentation to ensure compatibility with future releases.

image taken from: https://nextjs.org/docs/app/getting-started/project-structure

pages directory:

The traditional pages the directory was introduced in the first release of Next.js, which was Next.js 1.0 in October 2016. It was part of the foundational design of Next.js, showcasing its core concept of file-based routing.

Highlights from the Introduction:

• Each file in the pages directory automatically mapped to a route, simplifying the process of defining application routes.

• Dynamic routes and API routes were added in subsequent updates, further enhancing the functionality of the pages directory.

The pages directory became a hallmark feature of Next.js and remained the default for several years until the app directory was introduced in Next.js 13 (released in October 2022). This newer approach offered enhanced capabilities while retaining backward compatibility with the traditional pages directory.

In Next.js, the introduction of the src/app directory marks a shift from the traditional pages directory, bringing new features and concepts. Here's a breakdown of the differences between the two:

1. Routing

• pages Directory (Traditional)

  • Each file inside the pages directory automatically creates a route. For example, pages/index.js corresponds to the root route (/), and pages/about.js corresponds to /about.

  • Dynamic routes are created using file names wrapped in square brackets, such as pages/[id].js.

• src/app Directory

  • The app directory introduces file-based routing with an emphasis on layouts, templates, and more advanced routing features like nested routes and server components.

  • It's more flexible in terms of layouts and components that can be shared across routes. You can define layouts within this directory to wrap parts of your app with specific UI structures.

2. Folder Structure

• pages Directory

  • The pages directory contains only the pages of your application.

  • It’s a flat structure where the page names are directly tied to routes.

• src/app Directory

  • The app directory allows you to structure your app more modularly.

  • It can include layouts, templates, pages, components, and other application-related files, making it a more holistic directory for managing the whole application.

  • app also supports the concept of nested routing with layouts. For example, you can define a layout in app/layout.js and then define nested layouts for specific sections of your site.

3. Layouts and Nested Routes

• pages Directory

  • The traditional pages directory doesn’t have built-in support for layouts or nesting. While you can create shared layouts in components and include them in each page, this needs to be manually implemented.

• src/app Directory

  • The app directory supports nested layouts. You can define layouts that apply to multiple routes, which are inherited by child routes.

  • For example, you could have a layout for the entire app (e.g., app/layout.js), and inside any sub-folder (e.g., app/dashboard/layout.js), you could define a layout specific to that section.

  • Layouts in the app directory allow for more optimized rendering by React Server Components.

4. Server Components and Suspense

• pages Directory

  • The pages directory does not support React Server Components or Suspense out of the box. If you want to use them, you need to manage it manually.

• src/app Directory

  • The app directory natively supports React Server Components and Suspense. This allows for optimized server-side rendering and incremental static regeneration (ISR) to reduce client-side JavaScript bundle size and improve performance.

5. API Routes

• pages Directory

  • API routes are defined under pages/api/ (e.g., pages/api/hello.js for an API endpoint).

• src/app Directory

  • In the app directory, API routes are still defined within the pages/api folder. However, Next.js is evolving, and future versions may bring changes to how these API routes are structured in relation to the app directory.

6. File Naming and Conventions

• pages Directory

  • File naming in pages directly impacts routing. Each file corresponds to a route, and dynamic routes are defined using brackets (e.g., [id].js).

• src/app Directory

  • The file structure in the app directory follows a more modular approach, where files like layout.js, page.js, template.js, and error.js play key roles.

  • The concept of templates and error boundaries can be leveraged to control the UI structure across multiple pages or error handling for specific routes.

7. Static Site Generation (SSG) and Server-Side Rendering (SSR)

• pages Directory

  • You can use getStaticProps and getServerSideProps for static generation and server-side rendering respectively in the pages directory.

• src/app Directory

  • The app directory provides more advanced control over rendering with automatic static optimization, server-side rendering (SSR), and streaming support for layouts and pages.

The src/app directory offers a more advanced approach by providing modularity with layouts, templates, React Server Components, and support for Suspense. This directory provides scalability and flexibility when building larger applications that require dynamic layouts and advanced rendering techniques. It represents a modern method for structuring Next.js applications, especially when utilizing server-side rendering and the concurrent rendering features of React.