Using curl is one way: % curl -v https://google.com/ --http2 * Trying 2607:f8b0:4007:802::1008... * Connected to google.com (2607:f8b0:4007:802::1008)

Using curl is one way: % curl -v https://google.com/ --http2 * Trying 2607:f8b0:4007:802::1008... * Connected to google.com (2607:f8b0:4007:802::1008) port 443 (#0) * found 180 certificates in /etc/ssl/certs/ca-certificates.crt * found 722 certificates in /etc/ssl/certs * ALPN, offering h2 * ALPN, offering http/1.1 * SSL connection using TLS1.2 / ECDHE_ECDSA_AES_128_GCM_SHA256 ... * ALPN, server accepted to use h2 The above is with the GnuTLS build on Debian, recent enough OpenSSL versions support both NPN and ALPN.