Next.js: A Comparative Analysis of App Router and Pages Router

Next.js has established itself as a leading React-based framework for web development, offering server-side rendering, static site generation, and API routes. Two key features of Next.js are the App Router and the Pages Router. This article will take a detailed look at both, examining the benefits, limitations, and suitable use cases for each.

Pages Router: The Foundation of Next.js

The Pages Router has been an integral part of Next.js since its inception, offering a straightforward and reliable solution to routing. It uses client-side routing and is well-established and battle-tested, having been used in production by countless corporations.

The major advantage of the Pages Router is its maturity. It is robust, stable, and well-documented. It enjoys wide community support, meaning most issues and queries have been addressed online, making it a reliable option for many developers.

However, the Pages Router lacks certain features, such as the ability to handle nested layouts, error states, and loading states directly. Also, its client-side routing requires downloading the route map to the client, which can impact performance, especially in apps with many routes.

App Router: A Fresh Take on Next.js Routing

Introduced recently, the App Router marks a significant shift in the Next.js architecture. It builds on React Server Components and introduces features like nested layouts, error states, loading states, and even asynchronous components with top-level await, previously unheard of in Next.js.

App Router uses server-centric routing, meaning the route map doesn't need to be downloaded to the client, improving performance for apps with many different routes. While the routing is server-centric, the Link component enables client-side navigation, preventing a hard reload of the page when navigating between pages.

Another key feature is the App Router's caching strategy. It stores the payload of React Server Components in memory, improving the speed of navigating between already-visited pages. This granular caching approach wasn't possible with the Pages Router.

However, despite being marked stable and production-ready, the App Router has been criticized for some perceived early-stage issues. One of the main points of contention is its aggressive and complex caching system. While beneficial in many cases, this caching can pose challenges for highly dynamic apps, where the freshest content is required. Additionally, the caching approach can be confusing for developers new to the App Router, contributing to a steep learning curve.

Furthermore, not all tools compatible with the Pages Router are ready for the App Router. For example, the T3 stack, known for its full-stack type safety and productivity enhancement, is not yet compatible with the App Router.

Finally, early performance benchmarks suggest that the App Router might be slightly slower in terms of requests per second than the Pages Router. However, this might not necessarily be a bottleneck for overall application performance.

Conclusion: App Router or Pages Router?

The choice between the App Router and Pages Router depends on multiple factors such as the specific needs of the project, the familiarity of the developer with each router, and their risk aversion.

While the Pages Router offers reliability and familiarity, the App Router boasts superior features like React Server Components and granular caching.

If you're intrigued by the App Router's features and are willing to tackle its learning curve and early-stage issues, it's recommended to start using it. With the option of incremental adoption, you can always switch back to the Pages Router for specific pages if a feature doesn't work as expected.

Next.js is continually evolving, and both the Pages and App Router continue to offer promising paths for developing sophisticated web applications. It will be interesting to see how these tools evolve and how the developer community adapts to these changes. As always, the decision to use one or the other will ultimately depend on individual project requirements and developer preferences.