React — A JavaScript Library for User Interfaces

Tech Catalog / react.html

A Meta-built library for building web and native screens as components. Covers what it solves and where to start officially.

"What is React, and when should I use it?"

React is a JavaScript library for building user interfaces out of small reusable pieces called components. It is used for web browser screens and mobile app screens alike. It is maintained by Meta (formerly Facebook) as open source.

What problem does it solve

• It keeps large UIs manageable by splitting the screen into components.
• When data changes, React updates only the affected part instead of you rewriting the DOM by hand.
• It gives you one way of thinking about UI across web and mobile.

When it is a good fit

• Apps with heavy interaction and frequently changing state
• Projects built by several people (component-level collaboration)
• Projects that reuse many third-party UI packages

For a small static page, React is often more than you need.

Official starting points

• Install / start: the official docs' Quick Start uses the officially recommended tooling to scaffold a project.
• Learning order: Tutorial then Thinking in React works well for building intuition.
• Version: as of October 2026 the current major is React 19, with patches on the 19.2.x line. React 20 has not been announced.

Limits and caveats

• React is a library, not a full framework. Routing, data fetching, and similar concerns are chosen as separate packages.
• Tutorials outside the official docs may target older versions (pre-React 17). Check the version when picking learning material.
• The ecosystem moves fast, so the official blog's release posts are the safest way to judge freshness.

Next steps

• Concepts: the official docs' Quick Start (see sources below)
• Practice: finish the Tutorial end to end
• Apply: move one part of an existing page into components

Verified date indicates freshness. Check applicability conditions for older material.