Free · without registration
Check HTTP/2 and HTTP/3 of your website
Check the protocol support of your HTTPS address. The tool separates a successful HTTP/2 or HTTP/3 connection from a mere HTTP/3 announcement in the response header.
Start of test
Their results
Announcement and actual connection
A server can announce HTTP/3 via Alt-Svc. This does not yet prove that a QUIC connection is possible from the test location. For HTTP/2, the negotiation is evaluated via TLS. HTTP/3 is only actively tested if the cURL installation of the test server supports HTTP/3. If this capability is missing, the result is explicitly left open instead of devaluing the target server.
Why HTTPS and the exact host are important
Protocol support may differ between www, main domain, CDN and other subdomains. The checker therefore does not follow any forwarding and looks at the entered host. Check a forwarded destination address separately. The query uses HEAD; an HTTP error can also confirm a successfully established protocol connection.
A failed HTTP/3 test
HTTP/3 uses QUIC over UDP. Network filters, firewalls, routing and server configuration can prevent the connection. A failed setup therefore does not prove for sure that the service does not support HTTP/3 in principle. If necessary, compare the display in a current browser and control CDN and firewall settings.
Protocols do not replace performance analysis
HTTP/2 and HTTP/3 can support the transfer, but do not solve oversized images, slow backend responses or blocking scripts. The checker does not give a blanket SEO advantage for a protocol version. Connect the result with the investigation of real charging problems. The active selection takes place according to the cURL documentation for HTTP versions.
Example of classification
Alt-Svc contains h3, but the test server does not have QUIC support: the announcement is displayed; HTTP/3 remains “active measurement unavailable” and is not displayed as confirmed.
Frequent questions
Why is HTTP/3 open?
Either the test server does not support the active measurement or the connection could not be clearly confirmed.
Does the tool check the forwarding targets?
No. Each HTTPS address is tested without forwarding so that the result remains associated with the entered host.
Is HTTP/3 alone a ranking factor?
The tool does not derive a ranking rating from a protocol version. Decisive is the actual website quality and usage experience.