HTTP/2 & HTTP/3 Checker

Check if a website supports HTTP/2, HTTP/3, and Alt-Svc.

HTTP/2 and HTTP/3 are modern protocols that significantly improve website loading speed compared to HTTP/1.1. Our protocol checker tests whether a website supports these advanced protocols, checks for HTTP/3 support via Alt-Svc, and reports the negotiated HTTP version.

Result

Enter a URL to check HTTP protocol support.
In Action

HTTP/2 Checker in action

Your site feels slow in Lighthouse tests despite small pages. The checker reports HTTP/1.1 — your CDN config never enabled protocol upgrades. Flipping one toggle moves you to HTTP/2 and the next test shows the improvement in real numbers.

Frequently Asked Questions

What is the difference between HTTP/2 and HTTP/3?

HTTP/2 improves speed with multiplexing and header compression. HTTP/3 uses QUIC over UDP for even faster connections.

How do I check if a website uses HTTP/2 or HTTP/3?

Enter the URL and the tool reports the negotiated protocol: HTTP/1.1, HTTP/2, or HTTP/3 (QUIC). It also shows whether the server advertises Alt-Svc headers for protocol upgrades.

Why does my site still serve HTTP/1.1?

The usual causes: an old server or reverse proxy that predates HTTP/2, or the site is not behind HTTPS (browsers only use HTTP/2 and HTTP/3 over TLS). Enabling HTTPS is the first step; modern servers then enable HTTP/2 automatically.

What speedup can I expect from HTTP/2?

HTTP/2 multiplexes many requests over one connection and compresses headers. On typical pages with 30-80 resources, loading improves 15-40%. HTTP/3 adds faster connection setup and better performance on lossy mobile networks.