HTTP/2 and HTTP/3 Checker
This free HTTP/2 checker connects to your site over HTTPS, asks for HTTP/2 through the TLS ALPN handshake and reports the protocol the server really used. It also checks the Alt-Svc header for HTTP/3 (h3) support and tests whether the server accepts TLS 1.3 and TLS 1.2, so you can see whether the connection is modern.
HTTP/2 Checker
Technical SEO
About this tool
HTTP/2 lets a browser load many files over one connection at the same time, which removes much of the delay of the older HTTP/1.1 protocol on pages with many images, scripts and styles. HTTP/3 goes further by running over QUIC instead of TCP, which helps on weak mobile networks. Most browsers support both, and most good hosts and CDNs offer them at no extra cost.
The checker requests your page with HTTP/2 enabled and reads the version of the protocol that was actually negotiated. Browsers agree on HTTP/2 during the TLS handshake through a feature called ALPN, so a result of HTTP/1.1 means the server did not offer h2. For HTTP/3 the tool reads the Alt-Svc header, where a server announces that h3 is available. It then tries TLS 1.3 and TLS 1.2 handshakes.
A few limits apply. Our server cannot speak QUIC, so HTTP/3 is judged only from the Alt-Svc announcement, not from a real HTTP/3 request. Older TLS versions such as 1.1 and 1.0 are not tested. A CDN in front of your site decides the result for visitors, so test the live address, not the origin server directly.
Frequently asked questions
Does HTTP/2 improve SEO?
Not directly, since Google does not rank by protocol. HTTP/2 can make pages load faster, especially with many assets, and faster pages score better on Core Web Vitals and keep visitors. Googlebot can crawl over HTTP/2 too. It is a speed upgrade worth having rather than a ranking switch.
How do I enable HTTP/2 on my server?
HTTP/2 needs HTTPS. On Nginx add http2 to the listen 443 ssl directive. On Apache load mod_http2 and add Protocols h2 http/1.1. On shared hosting or a CDN such as Cloudflare it is usually already on or a single switch in the control panel.
What does Alt-Svc h3 mean?
The Alt-Svc response header tells browsers that the same site is also reachable over another protocol. A value starting with h3 means the server offers HTTP/3 over QUIC. The browser tries it on a later visit and falls back to HTTP/2 if it fails, so advertising h3 is safe.
Why does the result say HTTP/1.1 for a site that uses a CDN?
Some CDN plans, custom ports or load balancers do not offer h2 on every hostname, and a proxy in front of the origin may speak only HTTP/1.1. Check that HTTP/2 is switched on for the exact hostname, including the www and non-www versions, and that TLS is terminated by the CDN.