HTTP/2 & HTTP/3 Checker Tool Online

Last updated: May 29, 2026

Check whether a URL uses HTTPS and advertises HTTP/3. Get practical protocol notes for faster delivery, stronger trust, and GEO-friendly performance signals.

Enter a URL to check protocol signals:

How the HTTP Version Checker Works

The tool fetches your URL and reviews public response signals that a serverless environment can safely expose.

URL safety check, the host is validated before the request is made.
HTTPS check, the final URL is inspected after redirects.
HTTP/3 advertisement, the alt-svc header is scanned for h3 support.
Server notes, the response server header and detection limits are returned.

Why HTTP Protocols Matter

Modern transport protocols make asset delivery more efficient, especially on mobile and high-latency networks.

HTTPS trust, secure delivery is a baseline for SEO, forms, analytics, and browser features.
HTTP/2 efficiency, multiplexing helps reduce the old connection limits of HTTP/1.1.
HTTP/3 resilience, QUIC can improve connection behavior on unstable networks.
Performance stack fit, protocols work best with optimized CSS, JavaScript, images, and Astro rendering.

Protocol Benefits Table

Protocol	Benefit	What to verify
HTTPS	Trust and secure transport	All HTTP requests redirect to HTTPS.
HTTP/2	Multiplexed asset delivery	Confirm through CDN dashboard, browser devtools, or curl locally.
HTTP/3	QUIC transport for modern clients	Look for h3 in the alt-svc response header.

For stack choices that improve delivery speed, read what Astro is and our website performance optimization guide.

Next steps

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HTTP/2 and HTTP/3 Checker: FAQ

What does the HTTP/2 and HTTP/3 Checker test?

It checks whether a URL ends on HTTPS, whether an HTTP URL redirects to HTTPS, whether the server advertises HTTP/3 through the alt-svc header, and which server header is exposed.

Can Fetch prove HTTP/2 support?

No. Serverless Fetch APIs do not expose the negotiated HTTP protocol. The tool is honest about this limitation and focuses on HTTPS redirects plus HTTP/3 advertisement.

How is HTTP/3 detected?

Modern servers advertise HTTP/3 through an alt-svc response header containing h3. This means the browser may use HTTP/3 on a future connection if supported.

Does HTTP/2 improve performance?

HTTP/2 can improve multiplexing, header compression, and connection efficiency compared with old HTTP/1.1 patterns, especially on pages with many assets.

Does HTTP/3 improve Core Web Vitals?

HTTP/3 can reduce connection setup friction and improve reliability on unstable networks. It is not a replacement for optimizing images, JavaScript, CSS, and server response time.

Why does my CDN advertise HTTP/3 but my origin does not?

CDNs often terminate the browser connection and can advertise HTTP/3 even when the origin uses a different protocol behind the scenes.

Should every site use HTTPS?

Yes. HTTPS is required for modern browser features, trust, SEO quality, analytics integrity, and secure form submissions.

Is this HTTP version checker free?

Yes. It is a free online checker with no signup.

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