HTTP/2 Checker

We perform a TLS handshake on port 443 and check whether ALPN negotiates h2 (HTTP/2). If the server only offers http/1.1, HTTP/2 is not in use for that connection. You also get redirects, certificate, TLS version support, HTTP/3 advertisement, and security headers.

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Also try:

HTTP/3 Checker TLS 1.3 Checker HTTP/2 & HTTP/3 guide Full HTTPS check