WSGI (Web Server Gateway Interface) is a Python standard that defines how web servers communicate with web applications. It allows Python web applications (e.g., Flask, Django) to interact with web servers (e.g., Apache, Nginx, Gunicorn, uWSGI).
Key Features:
- Middleware Between Web Servers & Applications: Connects Python apps to web servers.
- Synchronous Processing: Unlike ASGI, WSGI does not support real-time features.
- Framework Compatibility: Works with Flask, Django, Pyramid, etc
- Single-Threaded by Default: Can be multi-threaded or multi-process with Gunicorn/uWSGI.
WSGI is a specification (PEP 3333) and not a framework or server.
How It Works
A WSGI server acts as a bridge between a web application and a web server.
WSGI Request Flow:
- Client (Browser/Postman) → Sends a request (e.g.,
GET /home). - Web Server (Apache/Nginx) → Receives the request.
- WSGI Server (Gunicorn/uWSGI) → Passes the request to the WSGI app.
- Python Web App (Flask/Django) → Processes the request and returns a response.
- WSGI Server → Web Server → Client → Sends the response back to the client.
In order to understand ASGI & WSGI standards better I suggest also watching this playlist