Express.js vs Next.js: What is the difference?

A little bit about each framework:

1) What is Express.js?

Express.js, or simply Express, is a backend web development framework for Node.js. It is intended for the development of web applications and APIs. It’s been dubbed Node.js’ de facto standard server framework.

This answer explains what Express is in greater detail.

2) What is Next.js?

Next.js is the React framework for production.

Let's debunk this sentence:

• "Framework": It has a lot of built-in features (e.g file-routing which replaces react-router-dom) that help you solve common problems.
• "For React": Next.js just enhances your React apps and adds more features to them.
• "For Production": There are certain problems that you will need to solve for almost all production-ready React apps. Next.js solves those for you.

Next.js gives you the best developer experience with all the features you need for production: hybrid static & server rendering, TypeScript support, smart bundling, route pre-fetching, and more. No config is needed.

Express.js vs Next.js features

Some Express.js features are:

• Robust routing
• HTTP helpers (redirection, caching, etc)
• View system supporting 14+ template engines

Next.js provides the following key features:

• Zero setup. Use the filesystem as an API ( You do not need Express to build a full-stack application)
• Server-Side rendering (SSR)
• Static site generation (SSG)
• Single-Page application (SPA)
• Development of faster applications
• Optimization of pages
• SEO websites
• Automatic code splitting

Conclusion

Express.js is a backend framework for building APIs whereas Next.js is a full stack framework that builds upon React to improve the SEO, development experience, and performance of your project. One of these features IS a built-in API routing system that could replace Express.js.

It all depends on the case you have and your personal preference. If you are building a private page (admin panel that can only be accessed with authentication) that does not need to be found by search engines, you do not need Next.js and will need Express.js. If you are building a public website (e.g. e-commerce website) and you are using Next.js for SEO optimization, you could replace Express.js with it.

TL;DR

You can replace an Express API with Next.js's API routing system but that only makes sense if you're building a full-stack React project. If it's a standalone API, using Next.js to replace just that API doesn't make any sense.