HTTP/2 & HTTP/3 Protocol Check
Checks support for HTTP/2 and HTTP/3 (QUIC) as well as ALPN latencies.
Guide & best practices
HTTP Protocol Check for HTTP/2, HTTP/3 and ALPN
Check the negotiated HTTP protocol versions and understand multiplexing, QUIC and protocol advertisement via Alt-Svc.
Typical use cases
Ideal for performance reviews, CDN/server migrations, HTTP/3 rollouts and verifying modern transport optimizations.
How Balou checks the HTTP protocol
Balou connects to the domain, determines the protocol version negotiated via ALPN and evaluates hints such as Alt-Svc and TLS version.
Modern protocol best practices
Enable HTTP/2 and ideally HTTP/3, advertise HTTP/3 via Alt-Svc and keep a modern TLS configuration as the baseline.
Frequently asked questions
What is the difference between HTTP/2 and HTTP/3?
HTTP/3 runs over QUIC on UDP and avoids the head-of-line blocking that can hit HTTP/2 at the TCP level during packet loss.
What is the Alt-Svc header for?
It advertises alternative protocols, e.g. h3=:443 with ma=86400, so clients use HTTP/3 next time.
What is ALPN?
Application-Layer Protocol Negotiation selects the protocol (e.g. h2 or http/1.1) during the TLS handshake.
Do I strictly need HTTP/3?
No, but it improves latency and connection setup especially on mobile and lossy networks.