Flask lets you choose your data layer, authentication, and frontend. Reflex brings a Python-authored interface, application state, and backend event handlers into one framework. Build a React-powered app without maintaining a separate handwritten React project.
A full-stack Python alternative to pairing Flask with a separately authored React frontend.
See how each framework approaches the frontend, data layer, authentication, and deployment.
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| Decision | Flask | Reflex |
|---|---|---|
| Data layer | No built-in ORM. Choose a database library or an extension such as Flask-SQLAlchemy, with migration tooling as needed. | Integrated SQLModel ORM and Alembic migrations, installed with the database extra. Connect an existing database after reviewing schema and migration ownership. |
| Authentication | Sessions are built in; user login and authorization are implemented in your app or added through extensions. | Integrate app authentication and enforce authorization in backend handlers. Reflex Enterprise offers a configured OIDC plugin under separate terms. |
| Frontend | Jinja templates with HTML, CSS, and JavaScript, or a separate frontend if your architecture calls for one. React is optional. | Author the interface in Python and generate a React frontend. Reflex handles communication between its UI and state; external services may still need APIs. |
| State and interactivity | Request/response routes and sessions. Add browser interactions with JavaScript and fetch without requiring a separate frontend framework. | Model user actions with Python event handlers and per-session state, synchronized with the browser over WebSockets. |
| Deployment | Run the Flask application on a production WSGI server. Frontend deployment depends on whether you use templates, static assets, or a separate app. | Deploy the generated frontend and Python backend with managed Reflex hosting or on your own infrastructure. |
Compare how the frameworks handle the frontend, data layer, authentication, and deployment. This is an architecture comparison, not a runtime performance benchmark.
Build a React-powered interface without maintaining it as a second codebase.
Reuse independent business logic and validation, or call your existing Flask services. Rebuild the screens and adapt request-bound logic to Reflex events. Specialized React components may still need JavaScript or TypeScript.
Reflex connects its interface to Python state and event handlers over WebSockets. You do not need to design a REST or GraphQL endpoint for every UI action. APIs remain useful for existing services and external integrations.
SellerX reported developing with Reflex ten times faster than with React and FastAPI. This is one team's experience with that stack, not a Flask or Django migration benchmark or a guaranteed improvement.
Read the SellerX storyReuse independent Python logic if you have it. Start clean if you don't.
01
Separate independent business logic and validation from Flask's request lifecycle. Keep existing service APIs where useful. Rebuild templates and UI-specific request handling as Reflex components and events.
02
Compose your pages, forms, and record views in Reflex. Map each user action to a Python event handler and make loading, validation, and failure states explicit.
03
Reconnect your data layer or existing APIs. Review Flask-Login, session handling, and authorization rules, then integrate authentication and enforce those rules in Reflex. Keep a single owner for schema migrations.
04
Test permissions, database writes, session behavior, realistic data volumes, and concurrent users. Deploy with Reflex or self-host, then move one workflow at a time.
Use managed Reflex hosting or run the frontend and Python backend on your own infrastructure: AWS, GCP, Azure, or on premises. Configure access controls, monitoring, backups, and capacity for your application.
Explore deployment optionsThe Apache 2.0 Python framework is available independently of Build and managed hosting. Your app still depends on Reflex and its other packages.
The AI development product generates and edits framework-based apps. Usage, private projects, repository access, and export entitlements belong to your plan.
Managed deployment is an operating service. You can also self-host a framework app, providing its frontend, Python backend, configuration, and maintenance.
Enterprise packages and services have separate entitlements. Workspace SSO is distinct from app-user authentication. Authorization, auditing, and private deployment need configuration and an agreed operating plan.
The practical details, before you make a move.
Flask is a production web framework with a deliberately extensible core. Choose Reflex when you want an interactive application whose UI, state, and backend behavior are authored together in Python, without assembling a separate React frontend.
Reflex provides SQLModel and Alembic integration through its database extra, so you do not need Flask-specific ORM extensions for a new Reflex app. Authentication is a separate integration decision, not an automatic Flask-Login replacement. Existing session and permission behavior needs to be mapped and tested.
Not just to connect Reflex's own interface to its Python state and event handlers. Reflex manages that communication over WebSockets. Existing Flask services, external clients, and partner integrations may still need authenticated APIs.
Yes. Keep Flask serving existing routes or APIs while Reflex provides new screens. Define how identity, data access, and errors cross the service boundary. Running both means operating both applications; whether that is transitional or permanent depends on your architecture.
Reflex lets you compose custom layouts, use CSS and Tailwind, wrap React components, and call Python libraries or services. It gives you an integrated component and state model rather than Flask's minimal core. Evaluate specialized extensions and request-bound code during a pilot.
Routes used by external consumers can remain in Flask. For screens you move to Reflex, rebuild templates and UI-specific route behavior as pages and event handlers. Reuse independent functions, but adapt code that depends on Flask's request context, sessions, or extensions.
Bring a workflow you want to improve, or start a new one. Build it with Reflex.
