Overview

Uvicorn 0.18, released on June 23, 2022, adopts watchfiles as reload backend and removes the asgiref dependency.

Main Features

watchfiles backend

Auto-reload now uses watchfiles (Rust-based) instead of watchgod, offering significantly better performance.

python 
# pip install uvicorn[standard]
# watchfiles is installed automatically

import uvicorn

uvicorn.run(
    'app:app',
    reload=True,  # uses watchfiles
    reload_delay=0.25,
)

Removed asgiref

The asgiref dependency has been removed, reducing the server footprint. Uvicorn handles the ASGI protocol directly.

python 
# Minimal Uvicorn 0.18 dependencies
# pip install uvicorn
# -> click, h11 (no asgiref)

# pip install uvicorn[standard]
# -> adds httptools, watchfiles, websockets, etc.

Sources