Does SSLcat support HTTP/3 and QUIC?

Q: Does SSLcat support HTTP/3 and QUIC?

SSLcat fully supports the HTTP/3 (QUIC) protocol, providing faster transfer speeds and better network performance, while also being backward compatible with HTTP/2 and HTTP/1.1.

Yes, SSLcat has full support for the HTTP/3 protocol (QUIC). This is one of the important technical features of SSLcat v1.3.16-rc10.

What are HTTP/3 and QUIC?

HTTP/3 is the third major version of the Hypertext Transfer Protocol. Unlike previous versions that relied on TCP, HTTP/3 uses QUIC, a new transport protocol built on top of UDP.

SSLcat's HTTP/3 Support

SSLcat implements HTTP/3 support through the quic-go library in Go:

Automatic Negotiation - The client and server automatically negotiate the best protocol to use
Backward Compatibility - Supports HTTP/2 and HTTP/1.1 simultaneously
TLS 1.3 - HTTP/3 uses the latest TLS 1.3 encryption
0-RTT - Supports 0-RTT connection resumption

Performance Advantages

Performance improvements of HTTP/3 compared to traditional protocols:

Faster Connection Establishment - Reduces the number of handshakes, lowering latency
More Efficient Multiplexing - Avoids head-of-line blocking issues
Network Switching Friendly - Performs better in mobile network environments
Congestion Control - More intelligent traffic control

Configuration Requirements

To enable HTTP/3, the following conditions must be met:

UDP Port - UDP port 443 must be open (shared with HTTPS)
Client Support - The browser needs to support HTTP/3
Network Environment - Some networks may restrict UDP traffic

Browser Support

Support for HTTP/3 in major browsers:

Chrome - Enabled by default since version 88+
Firefox - Enabled by default since version 88+
Safari - Supported since version 14+
Edge - Supported since version 88+

Practical Use Cases

HTTP/3 is particularly suitable for the following scenarios:

High-Latency Networks - Satellite networks, mobile networks
Loading Multiple Resources - Web pages with many images, CSS, and JS files
Real-Time Applications - Online gaming, video conferencing
CDN Acceleration - Content Delivery Networks

Monitoring and Debugging

SSLcat provides monitoring information related to HTTP/3:

Protocol Statistics - Shows the usage ratio of HTTP/1.1, HTTP/2, and HTTP/3
Connection Information - Displays the protocol version used by the client
Performance Metrics - Connection establishment time, transfer speed, etc.

Troubleshooting

If HTTP/3 is not working, possible reasons include:

Firewall Restrictions - Check if UDP port 443 is open
Client Not Supported - Use a newer version of the browser
Network Issues - Some network environments may block UDP traffic
Configuration Errors - Check if the SSLcat configuration is correct

You can check the actual protocol version used in the Network panel of your browser's developer tools.