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Performance & Tech tool
Detect HTTP/2 and HTTP/3 (QUIC) support by inspecting Alt-Svc headers and server fingerprints. HTTP/3 can reduce connection latency and support better Core Web Vitals on modern networks.
What it checks
Check if a website supports HTTP/2 or HTTP/3 (QUIC).
Inspect protocol, CDN, compression, and response signals where available.
Surface page weight, resource count, app shell clues, or installability signals.
Prioritize fixes that reduce latency, transfer size, or rendering friction.
Methodology
Next steps
Interpretation
Use cases
Find infrastructure or payload issues that can affect LCP, CLS, and INP.
Understand how a site is built, delivered, and optimized at the edge.
Retest after releases to catch heavier pages, slower responses, or missing compression.
Popular checks
Next paths
Use these pages when the result points to a broader check, a fix workflow, or a related technical question.
Frequently asked questions
No. Enter a URL or domain and run the check in your browser. Some results can be partial if the target site blocks requests or hides the data being checked.
The HTTP/3 & Protocol Checker runs live checks against the target website. Results reflect what was reachable at the time of the test, so retest after changing DNS, redirects, headers, or page content.
HTTP/3 is the latest HTTP protocol that uses QUIC instead of TCP. It reduces connection setup time, handles packet loss better, and improves performance especially on mobile networks.
HTTP/3 can reduce connection latency and help LCP and INP indirectly, especially on mobile or lossy networks. It is not a replacement for reducing JavaScript, optimizing images, and improving server response time.