Web Development · head to head
FastAPI vs Flask
FastAPI
Web Development
A modern, fast, high-performance web framework for building APIs with Python
- From
- Free
- Rated
- -
The short version
- Each has a real cost: FastAPI no built-in ORM, requires separate database libraries; Flask requires manual configuration of many common features like authentication, ORM, and admin panels
- Prices and features above were last checked on 30 August 2026.
Where they differ
Only the attributes on which FastAPI and Flask actually diverge.
Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Web Development).
What each one covers
Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.
Only in FastAPI
Nothing recorded that Flask does not also cover.
Only in Flask
- Lightweight framework
- Jinja2 templating
- Werkzeug WSGI toolkit
- URL routing
- Request handling
- Session management
- Cookie handling
- Blueprint organization
What people use each for
The jobs each tool is most often brought in to do.
FastAPI
- Building production-ready REST APIs with automatic validationnot Flask
- Serving machine learning model predictions as REST servicesnot Flask
- Building crisis management and orchestration platformsnot Flask
- Enabling real-time APIs with WebSocket connectionsnot Flask
- Rapid API development reducing boilerplate code significantlynot Flask
Flask
- REST APIs and backend servicesnot FastAPI
- Small-to-medium web applications and prototypesnot FastAPI
- Microservicesnot FastAPI
- Server-rendered apps using Jinja templatingnot FastAPI
- Teaching and learning web developmentnot FastAPI
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
FastAPI
- No built-in ORM, requires separate database libraries
- Python-only, cannot build with other languages
- Async/await learning curve for developers new to async programming
- Production deployment requires separate ASGI server configuration
Flask
- Requires manual configuration of many common features like authentication, ORM, and admin panels
- No built-in admin interface or scaffolding tools
- Minimal built-in security features compared to full frameworks
Pricing, plan by plan
FastAPI
FreeNo published plan breakdown. See the FastAPI review.
Flask
Free- Open SourceFree
- Micro web framework
- Flexible architecture
- Jinja2 templating
Which should you pick?
Choose Flask if
- You need lightweight framework.
- You want to start without paying.
- You work on Linux, macOS, Windows, Cloud (any platform supporting Python).
- You also want jinja2 templating.
Questions people ask
- Is FastAPI or Flask better?
- Neither clearly leads. FastAPI starts at Free and Flask at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, FastAPI or Flask?
- FastAPI starts at Free and Flask at Free.
- Does FastAPI or Flask run on more platforms?
- FastAPI runs on Web. Flask runs on Linux, macOS, Windows, Cloud (any platform supporting Python).
- Can I use FastAPI for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is FastAPI best used for?
- FastAPI is most often used for building production-ready rest apis with automatic validation, serving machine learning model predictions as rest services, building crisis management and orchestration platforms, enabling real-time apis with websocket connections. Of those, building production-ready rest apis with automatic validation and serving machine learning model predictions as rest services are not what Flask is typically brought in for.
- What can FastAPI do that Flask cannot?
- Flask covers Lightweight framework, Jinja2 templating, Werkzeug WSGI toolkit, URL routing.
Answered from the vendors’ own pages
FastAPI: Is FastAPI free to use?
Yes. FastAPI is free and open-source under the MIT License. It costs nothing to download, use, or deploy in production. An optional paid service, FastAPI Cloud, offers one-command deployment for additional convenience, but the core framework is free.
SourceFlask: Is Flask free to use?
Yes. Flask is open-source software released under the BSD-3-Clause License, available free for any use including commercial applications.
SourceFastAPI: Can I use FastAPI for commercial applications?
Yes. FastAPI's MIT License permits unrestricted commercial use, modification, and distribution. You can build and sell products powered by FastAPI without licensing fees or restrictions.
SourceFlask: What are Flask's core dependencies?
Flask depends on three main libraries: Werkzeug (WSGI toolkit), Jinja (template engine), and Click (CLI toolkit).
SourceFastAPI: Does FastAPI include a database or ORM?
No. FastAPI does not include a built-in database or ORM. You must add separate libraries like SQLAlchemy for database access. This gives flexibility to choose the database solution best suited to your project.
SourceFlask: Does Flask provide built-in database support?
No. Flask is a microframework that does not include built-in database support. Developers must choose and integrate their own database libraries, though Flask-SQLAlchemy is a popular community extension.
SourceFastAPI: What Python versions does FastAPI support?
FastAPI supports Python 3.7 and later. Older Python versions are not compatible, so you must run at least Python 3.7 to use FastAPI.
SourceFlask: What platforms does Flask support?
Flask is a microframework for Python that runs on any platform that supports Python, including Linux, macOS, Windows, and cloud platforms.
SourceFlask: Can Flask scale to large applications?
Yes. While designed to be lightweight and simple, Flask is designed with the ability to scale up to complex applications through blueprints, extensions, and modular architecture.
SourceFlask: Does Flask require a build step to run?
No. Flask does not require a build step. Applications can run directly with the Flask development server using 'flask run' from the command line.
SourceRelated pages
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