Web Development · head to head
Flask vs FastAPI
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: Flask requires manual configuration of many common features like authentication, ORM, and admin panels; FastAPI licensed under the MIT License per fastapi.tiangolo.com; as open source software it has no paid tier or vendor price to compare
Where they differ
Only the attributes on which Flask and FastAPI 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 Flask
- Lightweight framework
- Jinja2 templating
- Werkzeug WSGI toolkit
- URL routing
- Request handling
- Session management
- Cookie handling
- Blueprint organization
Only in FastAPI
Nothing recorded that Flask does not also cover.
What people use each for
The jobs each tool is most often brought in to do.
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
FastAPI
No use cases recorded yet. See the FastAPI review.
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
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
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
Pricing, plan by plan
Flask
Free- Open SourceFree
- Micro web framework
- Flexible architecture
- Jinja2 templating
FastAPI
FreeNo published plan breakdown. See the FastAPI review.
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 Flask or FastAPI better?
- Neither clearly leads. Flask starts at Free and FastAPI at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Flask or FastAPI?
- Flask starts at Free and FastAPI at Free.
- Does Flask or FastAPI run on more platforms?
- Flask runs on Linux, macOS, Windows, Cloud (any platform supporting Python). FastAPI runs on Web.
- Can I use Flask for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Flask best used for?
- Flask is most often used for rest apis and backend services, small-to-medium web applications and prototypes, microservices, server-rendered apps using jinja templating. Of those, rest apis and backend services and small-to-medium web applications and prototypes are not what FastAPI is typically brought in for.
- What can Flask do that FastAPI 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.
SourceFlask: What are Flask's core dependencies?
Flask depends on three main libraries: Werkzeug (WSGI toolkit), Jinja (template engine), and Click (CLI toolkit).
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.
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
Other head to heads
- Flask vs Django
- Flask vs MySQL
- Flask vs Next.js
- Flask vs Laravel
- Flask vs npm
- Flask vs React
- Flask vs Vue.js
- Flask vs Nginx
- Flask vs Node.js
- Flask vs v0 by Vercel
- Flask vs Apache HTTP Server
- Flask vs Astro
- Flask vs Bolt.new
- Flask vs Carrd
- Flask vs .NET
- Flask vs Express.js
- Flask vs NestJS
- FastAPI vs Django
- FastAPI vs MySQL
- FastAPI vs Next.js
- FastAPI vs Laravel
- FastAPI vs npm
- FastAPI vs React
- FastAPI vs Vue.js
- FastAPI vs Nginx
- FastAPI vs Node.js
- FastAPI vs v0 by Vercel
- FastAPI vs Apache HTTP Server
- FastAPI vs Astro
- FastAPI vs Bolt.new
- FastAPI vs Carrd
- FastAPI vs .NET
- FastAPI vs Express.js
- FastAPI vs NestJS