Reflex

Reflex (formerly Pynecone) is an open-source, full-stack Python framework for building complete web applications, frontend and backend, entirely in Python. Where Streamlit reruns a script and Dash wires callbacks, Reflex is structured like a web framework: pages are built from components, state lives in Python classes, and event handlers are Python methods.

Under the hood, Reflex compiles components into a React app (built with Vite and React Router since version 0.8) and runs a Python backend that holds each user's state. The browser and the backend stay in sync over a WebSocket, so an event handler changes state in Python and the affected components re-render in the browser. The component library is built on Radix UI, and any React component can be wrapped for use from Python.

The framework covers routing, forms, file uploads, background tasks, and a built-in database layer on SQLAlchemy, which makes it suited to dashboards, internal tools, and customer-facing apps that would otherwise need a separate JavaScript frontend. Authentication comes from integrations such as Auth0 and Clerk rather than a built-in system.

Reflex is free under the Apache 2.0 license and self-hosts anywhere a Python server and static files can run. The Reflex team also runs Reflex Cloud, a hosting platform with an AI app builder, with a free plan and paid Pro plans.