Comparing
FastAPI framework, high performance, easy to learn, fast to code, ready for production
A simple framework for building complex web applications
| Metric | fastapi | flask |
|---|---|---|
| Ecosystem | Python | Python |
| Difficulty | Beginner | Beginner |
| Weekly downloads | 0 | 0↑ |
| Latest version | v0.135.2 | v3.1.3 |
| Recipes | 1 | 1 |
fastapi only
Shared
flask only
Use FastAPI when building REST or GraphQL APIs in Python, especially when you need async support, automatic OpenAPI/Swagger docs, request validation, or are building microservices. It's the best choice for new Python API projects.
Use Flask for small-to-medium web apps and APIs where you want to control the stack, for prototypes where you need something running fast, or when teaching web development concepts without the complexity of Django.
FastAPI is API-only — it has no templating, admin interface, or ORM. For full-stack web apps with server-rendered HTML, Django is better. For tiny internal tools, Flask's smaller learning curve might be preferable.
Flask becomes painful as an app grows — you end up assembling Django yourself from extensions. For async APIs, FastAPI is a better starting point. For anything needing built-in auth, admin, or ORM, Django pays off faster.
fastapi
flask