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Software · head to head

FastAPI vs Flask

F

FastAPI

Software

A modern, fast, high-performance web framework for building APIs with Python

From
Free
Rated
-
Full reviewWebsite
Flask logo

Flask

Software

A lightweight WSGI web application framework

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: FastAPI licensed under the MIT License per fastapi.tiangolo.com; as open source software it has no paid tier or vendor price to compare; Flask requires manual configuration of many common features like authentication, ORM, and admin panels

Where they differ

Only the attributes on which FastAPI and Flask actually diverge.

Attributes where FastAPI and Flask differ
AttributeFastAPIFlask
Pricing modelopen-sourcefree
PlatformsWebLinux, macOS, Windows, Cloud (any platform supporting Python)
FoundedUnknown2010

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Unknown).

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

No use cases recorded yet. See the FastAPI review.

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

  • Licensed under the MIT License per fastapi.tiangolo.com; as open source software it has no paid tier or vendor price to compare
  • FastAPI depends entirely on Starlette for its web layer and Pydantic for validation, per its own documentation, so it is not a standalone framework and inherits both dependencies' constraints

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

Free

No published plan breakdown. See the FastAPI review.

Flask

Free
  • Open SourceFree
    • Micro web framework
    • Flexible architecture
    • Jinja2 templating

Which should you pick?

Choose FastAPI if

  • You want to start without paying.
FastAPI review

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.
Flask review

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 can FastAPI do that Flask cannot?
Flask covers Lightweight framework, Jinja2 templating, Werkzeug WSGI toolkit, URL routing.

Answered from the vendors’ own pages

Flask: 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.

Source
Flask: What are Flask's core dependencies?

Flask depends on three main libraries: Werkzeug (WSGI toolkit), Jinja (template engine), and Click (CLI toolkit).

Source
Flask: 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.

Source
Flask: 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.

Source
Flask: 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.

Source
Flask: 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.

Source
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