How to host FastAPI applications

1. Prerequisites

• Square Cloud Account: Create your account via the Registration Page (Email or GitHub).
• Active Plan: A paid plan is required for hosting. Check the pricing here.

2. Network Configuration

For your API to be externally accessible, the web server must be configured to operate on port 80. Unlike local environments (where we use 8000), Square Cloud uses port 80 for public routing.

Code Structure Example (app/main.py)

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"status": "online", "framework": "FastAPI"}

3. Performing the Deployment

1. Project Cleanup: Remove cache folders like __pycache__ or virtual environment folders (.venv).
2. Compression: Create a .zip file containing your code folder (e.g., app/) and the requirements.txt file.
3. Upload: In the Square Cloud Dashboard, upload the .zip file.
4. Web Publishing: During submission, locate and check the "Publish to Web" option.
5. Subdomain: Define the name of your free subdomain (e.g., my-api.squareweb.app).
6. Production Start Command: FastAPI now features a built-in CLI command that simplifies production execution, ensuring that the server utilizes workers efficiently and listens on the correct port.

At the time of upload or in your squarecloud.app file, set the start command to:

python -m fastapi run app/main.py --port 80

• run: Command optimized for production execution.
• app/main.py: The path to the file where your FastAPI instance is located.
• --port 80: Defines the mandatory port for functioning on Square Cloud.

5. Custom Domains (Standard+ Plan)

If you use the Standard plan or higher, you can configure a professional domain (e.g., api.yourdomain.com):

• The configuration is done in the Network tab of the Dashboard.
• SSL (HTTPS) is automatically generated, ensuring your API is secure by default.

6. Performance Tips

• Automatic Validation: FastAPI uses Pydantic for data validation. Make sure to define schemas to gain performance in JSON serialization.
• Environment Variables: Use the ENV tab in the Dashboard to manage security keys and database connections, accessing them via os.getenv().
• Monitoring: Follow real-time logs via the Dashboard to check the loading of the server workers.

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Updated on: 05/26/2026