Free tool

HTTP/1, HTTP/2 & HTTP/3 checker

Enter a website to see which HTTP versions it speaks — we negotiate HTTP/1.1, HTTP/2 and HTTP/3 (QUIC) live and report the protocol and response time for each.

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HTTP/1.1, HTTP/2 and HTTP/3

HTTP/1.1 opens a connection per request (or reuses one request-at-a-time), which can bottleneck pages with many assets. HTTP/2 multiplexes many requests over a single TLS connection, removing that head-of-line blocking at the application layer and adding header compression.

HTTP/3 moves the transport from TCP to QUIC over UDP, so packet loss on one stream no longer stalls the others and connections resume faster on flaky networks. Servers advertise HTTP/3 through the Alt-Svc response header, telling clients an h3 endpoint is available to upgrade to.

This checker negotiates each version against the site over HTTPS and reports what the server actually speaks, so you can confirm a CDN or origin is serving the protocols you expect.