You’ve probably seen the terms React, React.js, and ReactJS used interchangeably—and that’s because in most casual contexts, they all refer to the same thing.

But here's a clear breakdown so you understand the subtle differences and naming conventions:

1. React

Official Name: This is the correct and most common name used by the developers at Meta (formerly Facebook), who created the library.

• React refers to the open-source JavaScript library used for building user interfaces, especially single-page applications (SPAs).
• When in doubt, use React—it’s the name used in the official documentation and in most professional conversations.

2. React.js

Technical Extension: The “.js” part just emphasizes that React is a JavaScript library.

• Sometimes developers write React.js to be more specific, especially in URLs, filenames, blog titles, or SEO.
• For example, you might see filenames like react.min.js in a codebase or CDN.

You can think of React.js as synonymous with React—it's not incorrect, just a bit more descriptive.

3. ReactJS

Search Engine Friendly Version: This version is mostly used in online searches, blogs, or domain names.

• For example, you’ll often see people searching "ReactJS tutorial" or "ReactJS vs AngularJS".
• It’s also used in the official React website’s domain: reactjs.org, which helps differentiate it from other "React" terms that might exist outside of programming.

So don’t worry—whether someone says React, React.js, or ReactJS, they’re all talking about the same awesome library for building modern UIs.