Swagger UI & ReDoc in FastAPI 🚀

FastAPI automatically generates interactive API documentation using Swagger UI and ReDoc. These tools help developers test APIs, explore endpoints, and understand request/response formats.

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🔹 What is Swagger UI?

Swagger UI provides an interactive interface where developers can: ✅ View API endpoints
✅ Send requests (GET, POST, PUT, DELETE)
✅ See request & response formats
✅ Authenticate APIs using tokens

📌 Access Swagger UI in FastAPI
When you run a FastAPI app, visit:
👉 http://127.0.0.1:8000/docs

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🔹 What is ReDoc?

ReDoc is an alternative documentation tool that provides a clean, structured API reference.
✅ Better readability
✅ Supports Markdown descriptions
✅ Great for large APIs

📌 Access ReDoc in FastAPI
👉 http://127.0.0.1:8000/redoc

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🔹 Example: FastAPI with Swagger UI & ReDoc

Let's create a simple FastAPI app.

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

# Request body model
class Item(BaseModel):
    name: str
    price: float

@app.get("/items/{item_id}")
async def get_item(item_id: int):
    return {"item_id": item_id, "name": "Sample Item"}

@app.post("/items/")
async def create_item(item: Item):
    return {"message": "Item created", "item": item}

Running the App

uvicorn main:app --reload

Open API Docs

🔹 Swagger UI → http://127.0.0.1:8000/docs
🔹 ReDoc → http://127.0.0.1:8000/redoc

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🔹 Customizing Swagger UI & ReDoc

FastAPI allows customization of Swagger UI & ReDoc.

📌 Custom API Title & Description

app = FastAPI(
    title="My FastAPI App",
    description="A simple API with Swagger & ReDoc documentation",
    version="1.0.0"
)

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📌 Disabling Swagger UI or ReDoc

Disable Swagger UI:

app = FastAPI(openapi_url="/openapi.json", docs_url=None)

Disable ReDoc:

app = FastAPI(redoc_url=None)

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🎯 Summary

• Swagger UI → Best for interactive API testing.
• ReDoc → Best for detailed API documentation.
• FastAPI automatically generates both at /docs & /redoc.
• Customization is possible via FastAPI parameters.