What is Express.js?

Express.js is a minimal, unopinionated web application framework for Node.js. It provides a thin layer of fundamental web application features — routing, middleware, request/response handling — without obscuring the underlying Node.js HTTP module. It is the most popular Node.js framework and forms the foundation for many other frameworks like Nest.js and Sails.js. Express makes it easy to build RESTful APIs, web servers, and microservices with very little boilerplate. Its minimalist design means you choose your own tools for databases, authentication, templating, and validation, giving you maximum flexibility.