Reflex

Reflex takes JavaScript out of the equation for Python developers building web apps. Frontend and backend are written in one language, in one file for a small app, so there is no separate client project, no API contract to keep in sync between halves, and no build toolchain to learn first.

The model is state plus events. A class inherits from the framework's state object and holds the app's data as typed attributes, event handlers mutate that state, and components declared as Python function calls re-render when it changes. An async handler can yield partway through to update the interface while slower work continues, which is how a loading state appears without extra plumbing.

Getting an app running takes a handful of commands.

• Project setup: create a directory, add reflex with uv, then run init and run.
• Local server: the development app serves on port 3000 straight away.
• Fast refresh: saved changes show up immediately, with no manual restart.
• Python components: headings, inputs, buttons and images are function calls, not templates.
• Room to grow: the framework stays approachable for a first app while scaling to complex ones.

Around the open source library the maintainers offer an AI builder that generates full-stack apps, an agent toolkit that connects MCP and skills to a coding assistant, and a hosting service for deployment and app management. A published architecture write-up explains what happens under the hood for anyone who wants the details first.