What is horizon?

Horizon (originally called Fusion during development) is an open-source backend platform for building realtime web applications with JavaScript. It is built on top of RethinkDB, a database designed to push live data updates to applications as changes happen. The project's main goal is to let front-end developers build modern, connected apps without having to write any server-side code from scratch. The platform has two parts working together. The server component runs alongside RethinkDB and handles all the data operations, acting as a bridge between the database and the browser. The client library is a small JavaScript package that developers include in their front-end code to communicate with that server. Together they let a browser tab read and write data, and receive live updates when other users change something, all without the developer needing to set up their own API routes or server logic. The services Horizon planned to expose include live data streaming, user authentication through providers like Google or GitHub, user account management, permission controls to restrict data access, and presence detection to track whether a user is online. These cover the common building blocks that show up in most modern web applications. The project is designed to grow with an application. If a project stays simple, developers can use Horizon's API for everything. Once the app needs custom business logic that Horizon does not cover, developers can add their own backend code in Node.js, Python, or any other language, and that code can talk directly to RethinkDB with full access to its features. The README compares Horizon to Firebase and Meteor. Unlike Firebase, it is self-hosted and open-source. Unlike Meteor, it is a narrower tool that does not impose a particular front-end framework or full-stack structure.