Which Python web framework should you choose in 2026? Performance, features, ease of use, and real-world use cases compared.
| Feature | FastAPI | Flask | Winner |
|---|---|---|---|
| Performance | Very fast (async support) | Good (synchronous) | FastAPI |
| Automatic Docs (Swagger/OpenAPI) | Built-in, interactive | Requires extensions | FastAPI |
| Learning Curve | Medium (Pydantic + async) | Very easy | Flask |
| Async Support | Native (Starlette/ASGI) | Limited (extensions) | FastAPI |
| Dependency Injection | Built-in & powerful | Manual or extensions | FastAPI |
| Community & Ecosystem | Rapidly growing | Mature & huge | Flask (still) |
| Best For | APIs, microservices, ML endpoints | Small apps, prototypes, simple sites | Depends on project |
from fastapi import FastAPI
app = FastAPI()
@app.get("/items/{item_id}")
async def read_item(item_id: int):
return {"item_id": item_id}
from flask import Flask
app = Flask(__name__)
@app.route("/items/")
def read_item(item_id):
return {"item_id": item_id}
pip install fastapi uvicorn pydanticPro tip: Start new projects with FastAPI, migrate legacy Flask apps only when performance or async is needed.