A WebSocket replacement built on HTTP/3 and QUIC.
Async Python server framework for HTTP/3 + WebTransport (QUIC).
What WebSocket would look like if it was designed today.
from http3x import App
from http3x.wt import Session
app = App()
class Echo(Session):
async def on_stream(self, stream):
async for data in stream:
await stream.send(data)
app.wt.add("/echo", Echo)
app.run(host='::', port=4433, certfile="cert.pem", keyfile="key.pem")
pip install http3x
Streaming AI-style responses over HTTP/3 (WebTransport):
You: hello
AI:
h
he
hel
hell
hello 👋
This is NOT WebSocket.
This is native HTTP/3 streaming over QUIC.

See tests/wt_chat_stream.py and tests/wt_chat_stream.html for the complete example.
| Feature | WebSocket | http3x |
|---|---|---|
| Protocol | TCP | QUIC (HTTP/3) |
| Streams | Single stream | Multiplexed streams |
| Datagram | No support | Built-in datagram |
| Head-of-line blocking | Yes | No |
Simple HTTP/3 server with GET and POST endpoints:
from http3x import App
from http3x.h3 import Handler
app = App()
class ApiHandler(Handler):
async def get(self):
return {'status': 'ok'}
async def post(self):
return {'status': 'ok'}
app.h3.add('/h3', ApiHandler)
app.run(host='0.0.0.0', port=443, certfile="cert.pem", keyfile="key.pem")
Using curl with HTTP/3 support:
curl --http3-only -k https://localhost:443/h3
curl --http3-only -k -X POST -d "Hello, HTTP/3!" https://localhost:443/h3
See tests/h3_mini.py for the complete example.
More docs coming soon.
Contributions are welcome! Please visit the GitHub repository to contribute code, report issues, or suggest features.
This project is licensed under the Apache License 2.0. See the LICENSE file for details.