HTTP/3 Advertisement & HTTPS Checker

Last updated: Oct 2, 2026

Check whether a URL uses HTTPS and advertises HTTP/3. This checks public response signals; confirm the negotiated protocol separately in browser developer tools.

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.

HTTP/1.1 vs HTTP/2 vs HTTP/3 reference

Each protocol version changed how requests travel between the browser and server. This reference compares delivery differences. The checker only observes HTTPS and HTTP/3 Alt-Svc advertising; confirm negotiated HTTP/2 or HTTP/3 in a browser Network panel or compatible curl client.

Feature	HTTP/1.1	HTTP/2	HTTP/3
Multiplexing	No, one request per connection at a time	Yes, many streams over one connection	Yes, independent QUIC streams
Head-of-line blocking	Yes, at the request level	Removed at app level, but TCP packet loss still stalls all streams	Removed, one lost packet affects only its own stream
Transport	TCP	TCP	QUIC over UDP
Header compression	None, plain text headers	HPACK	QPACK
Connection setup speed	Slowest, separate TCP and TLS handshakes	Faster, one connection reused for all streams	Fastest, QUIC merges transport and TLS handshake, supports 0-RTT resumption

Protocol upgrades only help once the rest of the stack is lean. For a full review of hosting, caching, and Core Web Vitals, see our website speed and performance optimization service or request a free website audit.

Next steps

HTTP/3 & HTTPS Signals related tools and articles

Continue with the closest follow-up checks and guides based on this tool's topic, crawl intent, and optimization workflow.

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HTTP/2 and HTTP/3 Checker: FAQ

Can this tool prove that a site negotiated HTTP/2?

No. The serverless Fetch API used by the checker does not expose the negotiated protocol, so the HTTP/2 field is intentionally inconclusive. Use browser network protocol columns, curl with protocol reporting, or server logs for direct confirmation.

What does HTTP/3 advertised mean?

It means the final response included an Alt-Svc value containing an h3 token. That is evidence that the server or CDN advertises an HTTP/3 alternative, not proof that this request used HTTP/3 or that every visitor can connect with it.

Does no Alt-Svc header prove HTTP/3 is disabled?

No. Advertisement can vary by CDN edge, request, cached response, or deployment configuration. Some environments discover HTTP/3 by other means. Treat an absent header as not advertised to this check, then verify from a compatible client.

What HTTPS information does the check provide?

It reports whether the final URL is HTTPS and whether an originally HTTP URL ended on HTTPS after redirects. It also shows the final URL, status, Server header, Alt-Svc value, and elapsed server-side check time.

Does it show the entire HTTPS redirect chain?

No. The fetch follows redirects and reports the final URL plus a yes or no HTTPS-redirect flag. It does not list each intermediate hop or validate whether every redirect is permanent and canonical.

Why can the result differ by location or browser?

HTTP/3 and Alt-Svc are often controlled by a CDN and can vary by edge, client capability, cache, and network. This request originates from the checker's server environment, not from your browser connection.

What should I do with an inconclusive result?

First confirm HTTPS redirects correctly. Then check the protocol in a current browser or curl, inspect Alt-Svc at the edge, and review CDN or web-server settings. Measure real performance before treating a protocol label as an optimization by itself.

What data is sent to run this check?

The submitted URL is sent to Web Aloha's server, which fetches the public resource and returns protocol-related response signals. The endpoint does not include application logic that stores the response body or result, though infrastructure logs may record the request.

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