HTTP/2 test

Enter a domain and we open a real TLS connection and negotiate the protocol using ALPN, the same mechanism browsers use. You get a clear yes or no on HTTP/2, the protocol the server actually picked, the TLS version, and a hint about HTTP/3 from the Alt-Svc header.

How the HTTP/2 test works

HTTP/2 is negotiated during the TLS handshake using an extension called ALPN (Application-Layer Protocol Negotiation). The client offers a list of protocols, in our case h2 and http/1.1, and the server picks one. We perform exactly that handshake and report which protocol the server selected.

HTTP/2 brings multiplexing, header compression and request prioritisation over a single connection, which usually makes pages load faster, especially over high-latency links. It needs no changes to your site, only support on the server or CDN, so enabling it is one of the easiest performance wins available.

We also read the Alt-Svc response header, which is how servers advertise HTTP/3 (QUIC). If h3 appears there, the server supports HTTP/3 and capable browsers will upgrade to it automatically on the next visit. HTTP/3 runs over UDP and improves performance further on lossy or mobile networks.

Why HTTP/2 matters for performance and SEO

• Faster loads: one connection carries many requests in parallel without head-of-line blocking.
• Lower overhead: HPACK header compression shrinks repeated request headers.
• Better Core Web Vitals: faster delivery helps Largest Contentful Paint, a Google ranking signal.
• No downside: HTTP/2 falls back to HTTP/1.1 automatically for old clients.

Frequently asked questions