Frontity is a free and open-source framework for building WordPress websites using React.
Frontity is a free and open-source framework. It enables you to easily build a React-based frontend for a headless (or decoupled) WordPress site. Your WordPress site serves its data via the REST API, and the frontend that you build with Frontity consumes this data and renders it in the browser as a SPA (Single Page Application) which you can configure and style to your liking.
The above approach, as exemplified by Frontity, has many advantages. But in order to build a site in this way without Frontity there are a lot of things that developers need to learn and configure: bundling, transpiling, routing, server rendering, retrieving data from WordPress, managing state, or managing CSS, among many others.