Is ASGI a Web Server?


Larry Thompson

ASGI, which stands for Asynchronous Server Gateway Interface, is not a web server itself. Instead, it is a specification that defines how web servers and applications should communicate with each other in an asynchronous manner. This allows for more efficient handling of concurrent requests and better scalability.

What is ASGI?

ASGI was introduced as an evolution of the WSGI (Web Server Gateway Interface) standard, which has been widely used in the Python web development community for many years. While WSGI served its purpose well for synchronous web frameworks, it struggled to handle the increasing demands of modern web applications.

ASGI was designed to overcome these limitations by enabling asynchronous communication between web servers and applications. It allows multiple requests to be processed concurrently without blocking other incoming requests, resulting in improved performance and responsiveness.

How does ASGI work?

ASGI introduces the concept of an application server, which sits between the web server and the actual web application. The application server is responsible for receiving incoming requests from the web server and passing them on to the appropriate ASGI application.

An ASGI application can be thought of as a collection of asynchronous functions or coroutines that handle different aspects of request processing. These functions can perform I/O operations asynchronously, allowing other requests to be processed in parallel.

In addition to handling incoming requests, ASGI also supports bidirectional communication between the web server and application. This means that real-time updates can be pushed from the server to the client without requiring continuous polling or long-lived connections.

Benefits of using ASGI

  • Improved performance: By enabling asynchronous request handling, ASGI allows web servers to handle multiple concurrent requests efficiently. This results in faster response times and better overall performance.
  • Better scalability: ASGI’s asynchronous nature makes it easier to scale web applications horizontally by adding more servers.

    With traditional synchronous web frameworks, scaling can be challenging due to limitations in concurrent request handling.

  • Real-time capabilities: ASGI supports bidirectional communication, making it suitable for real-time applications such as chat systems or collaborative tools. This eliminates the need for continuous polling or long-lived connections.

ASGI-compatible web servers and frameworks

A number of web servers and frameworks have adopted the ASGI specification, allowing developers to build high-performance asynchronous web applications. Some popular ASGI-compatible web servers include Daphne, Uvicorn, and Hypercorn.

Frameworks like Django and FastAPI have also added support for ASGI, enabling developers to leverage its benefits while utilizing familiar tools and libraries.


In summary, ASGI is not a web server itself but rather a specification that defines how web servers and applications should communicate asynchronously. By enabling efficient handling of concurrent requests and bidirectional communication, ASGI offers improved performance, scalability, and real-time capabilities. Its adoption by various web servers and frameworks makes it a powerful tool for building modern web applications.

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