How do I get HTTP/3 with QUIC to work?

HTTP/3 with QUIC requires the following:

• Windows Server 2022 and above
• TLS 1.3
• TLS_CHACHA20_POLY1305_SHA256, TLS_AES_256_GCM_SHA384 and/or TLS_AES_256_GCM_SHA256
• Alt-Svc header in IIS
• Port 443 UDP open

The easiest way to enable HTTP/3 with QUIC is to use any of the built in templates like Best Practices or PCI 4.0. They will enable TLS 1.3 and add in the required cipher suites. After that, click on the Advanced tab and check Enable HTTP/3 with QUIC. Apply the settings and reboot.

Next open up the IIS Manager. Select the website and double click on HTTP Response Headers. Add in a header with the Name Alt-Svc and Value h3=":443"

Finally you will need to open up port 443 with UDP for incoming connections on the server and your firewall.

You can test out your site using HTTP/3 check.