FastAPI Quickstart in 2026

Source: Dev.to

What is FastAPI?

FastAPI is a modern Python framework for building RESTful APIs with high performance and minimal boilerplate. In 2026 it has become an industry standard thanks to its speed, reliability, automatic interactive documentation, and native support for asynchronous programming.

Installation

You can install FastAPI (including the standard set of optional dependencies) with either uv or pip:

# Using uv (a fast, Rust‑based package manager)
uv add fastapi[standard]

# Using pip
pip install fastapi[standard]

Creating a FastAPI app

Create a new file named main.py and add the following code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello, World!"}

Running the application

Start the development server with:

fastapi dev

When the server is running, open http://localhost:8000/ in a browser. You should see a JSON response similar to:

{
  "message": "Hello, World!"
}

Interactive documentation

FastAPI automatically generates OpenAPI documentation.

• Swagger UI: http://localhost:8000/docs – an interactive interface for testing endpoints.
• ReDoc: http://localhost:8000/redoc – a more formal, professional‑grade documentation view.

Conclusion

FastAPI provides a developer‑friendly ecosystem that handles much of the heavy lifting—from automatic documentation to asynchronous support—making the transition from a simple “Hello World” to a high‑performance, production‑ready API smooth and efficient.