Next.js 13 is a major release of the popular React framework that introduces several new features and improvements.

App Router and Server Components

One of the significant changes in Next.js 13 is the introduction of a new routing system called App Router. This new routing system is a complete rewrite of the previous one and coexists with the existing pages directory. The new App Router comes with a concept called Server Components (RSC), a new type of React component that runs on the server and returns compiled JSX to the client. Server Components are the default component type in the new app directory.

Layouts and Performance Improvements

Layouts are another important feature introduced in Next.js 13. They are foundational components that wrap pages and allow for displaying a common UI across pages and reusing logic and data fetching. Layouts also solve the waterfall problem that was present in the previous routing system and provide performance improvements.

Enhanced Router and Flexible Component Structure

The enhanced router in Next.js 13 allows for adding various types of components in the app directory using conventional filenames, enabling a more flexible and organized structure. Pages, layouts, errors, and loading states can be defined using specific filenames, contributing to a more flexible component structure.

Server Components and Constraints

Server Components, the new default component type in Next.js, run on the server and return compiled JSX to the client. They are useful for rendering the skeleton of a page, reducing the amount of JavaScript sent to the client, and improving routing performance for server-rendered pages. Server Components have some constraints, such as not being able to use browser-only APIs, React hooks, or Context.

Server Actions and Complex Logic

Server Actions, although still in the alpha stage, offer a new way to execute functions on the server without wiring them through an API handler. They are useful for executing server-side logic such as sending emails or updating a database. Server Actions can be used for submitting forms, executing server-side logic, and redirecting the user to a new page. They also provide the ability to revalidate data fetched from Server Components, eliminating the need for complex client-side state management.

Pages, Metadata, and Loading Indicators

Pages in the new app directory are defined with the page.tsx convention. Page metadata and SEO information can be specified using the metadata property, and dynamic data can be accessed using the generateMetadata function. Static pages can be generated using the generateStaticParams function. Loading indicators can be implemented using the loading.tsx file, which can be defined in every directory.

Conclusion

Next.js 13 brings significant improvements and new capabilities to the framework, making it even more powerful and efficient for building React applications. The new routing system, Server Components, enhanced router, layouts, and other features contribute to improved performance, code organization, and developer productivity.