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Detect HTTP/2 and HTTP/3 (QUIC) support by inspecting Alt-Svc headers and server fingerprints. HTTP/3 reduces latency and improves Core Web Vitals — find out if you're keeping up.
Best for
Use this tool when you need one sharp answer fast before opening a broader report.
The input and results are designed to stay readable and tappable on smaller screens.
This page targets both broad keywords and practical queries people use before they audit a specific domain.
Frequently asked questions
Yes — the HTTP/3 & Protocol Checker is 100% free with no signup, no account, and no usage limits. Just enter a URL and get instant results.
Our HTTP/3 & Protocol Checker runs live checks against the target website in real time. Results reflect the current state of the site at the moment you run the check — not cached or historical data.
HTTP/3 is the latest HTTP protocol that uses QUIC instead of TCP. It reduces connection setup time, handles packet loss better, and improves performance especially on mobile networks.
Yes — HTTP/3 can significantly reduce LCP and FID by eliminating TCP head-of-line blocking and reducing TLS handshake time from 3 round-trips to just 1.