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Free HTTP/3 & QUIC Test

Test whether your web server supports HTTP/3 over QUIC with a live handshake probe and verify its Alt-Svc discovery signal.

Also known as: HTTP/3 test, QUIC

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Run a real check above

Submit a public URL, domain, or keyword. Novaverb will show only the evidence this tool can actually retrieve or measure.

Evidence model

Know what the result proves

This check proves whether a real HTTP/3 request over QUIC succeeds, not merely whether HTTP/3 is advertised. Support is reported only when an actual h3 response comes back, so an Alt-Svc header pointing at an endpoint that never answers is reported as advertised and unconfirmed rather than as support.

1. Source

Live QUIC handshake + Alt-Svc. The result identifies where its evidence came from.

2. Boundary

This attempts a real QUIC connection offering ALPN h3 and also reads the Alt-Svc discovery signal. Confirmed means a live HTTP/3 handshake completed; advertised means h3 was announced but not confirmed here.

3. Next action

Use the finding to verify a problem, then connect a workspace when you need history, monitoring, or site-wide analysis.

What does an HTTP/3 test measure?

HTTP/3 carries HTTP over QUIC, a UDP-based transport. This checker first reads the live HTTPS discovery signal, then attempts a real QUIC handshake and HTTP/3 request. The result separates an advertised capability from a confirmed one.

How to enable HTTP/3

Enable QUIC on the public edge: Use a CDN or server that supports HTTP/3 and configure the public HTTPS hostname.
Allow UDP 443: Make sure network policy and firewalls allow QUIC traffic alongside normal HTTPS.
Advertise h3: Return an Alt-Svc h3 signal so compatible clients can discover the HTTP/3 endpoint, then retest.

If HTTP/3 is only advertised

Check UDP reachability, CDN edge policy, certificate/SNI configuration and whether the probe is being blocked. An Alt-Svc header alone does not prove that QUIC can complete.

What this test proves

A real QUIC + HTTP/3 handshake when confirmed, or a clearly labelled discovery signal when only h3 is advertised.

What it does not prove

It does not measure page speed, Core Web Vitals, every geographic edge, or HTTP/3 usage by all visitors.

RFC 9114, HTTP/3
RFC 9000, QUIC

"Confirmed" means a live HTTP/3 (QUIC) handshake completed; "Advertised" means h3 was announced via Alt-Svc but not confirmed by this check.

Get the right answer

What to submit - and what to avoid

Submit the domain or any URL on the site; only the origin is used. A private host is refused. Bear in mind that HTTP/3 travels over UDP, so a network that blocks QUIC will make a site that genuinely supports it look unsupported from that vantage point, which is a property of the path rather than of the server.

Use it like this

yourdomain.comAny address form works. http or https, with or without www, a bare domain or a full path - we normalize it for you.

https://www.yourdomain.comHTTP/3 rides on QUIC over UDP 443; we resolve the origin and try it directly.

Avoid this

Reading 'unsupported' as a tool errorIf UDP 443 is filtered on the path, a real h3 request cannot complete - 'unsupported' is then the correct finding, not a bug.

Public methodology

Exactly how this result is produced

The Alt-Svc header is read first, because that is how an h3 endpoint is discovered. A real HTTP/3 request is then attempted over QUIC against that endpoint, and the result is reported as supported only when an actual h3 response is received. Advertisement and confirmation are kept as separate findings throughout.

We read the Alt-Svc header that advertises an h3 endpoint for discovery.
We attempt a real HTTP/3 request over QUIC to confirm support, not just the advertisement.
We report supported only when an actual h3 response is received.

Built on public standards

The international standards this check applies

Three IETF specifications define this result. RFC 9114 defines HTTP/3, RFC 9000 defines the QUIC transport it runs on, and RFC 7838 defines the Alt-Svc header used for discovery. Separating discovery from confirmation follows directly from RFC 7838, which describes an advertisement rather than a guarantee.

IETFRFC 9114

HTTP/3

Completes a real HTTP/3 request to confirm support, not just an advertisement.

Read the specification

IETFRFC 9000

QUIC Transport

Opens a QUIC connection over UDP as the transport for HTTP/3.

Read the specification

IETFRFC 7838

HTTP Alternative Services (Alt-Svc)

Reads the Alt-Svc header that advertises an h3 endpoint for discovery.

Read the specification

We list a standard only where this tool genuinely reads or measures against it. Where a signal is outside a live check, the result says so instead of implying coverage.

Common questions

HTTP/3 Test FAQ

What does the Novaverb HTTP/3 Test confirm?

It attempts a real QUIC connection offering ALPN h3 to confirm your server actually speaks HTTP/3, and separately reads the Alt-Svc header to report whether an h3 endpoint is merely advertised.

What is HTTP/3?

HTTP/3 is the latest HTTP version, defined in RFC 9114, running over QUIC instead of TCP. QUIC uses UDP, integrates TLS 1.3, and eliminates TCP head-of-line blocking, improving performance on lossy or high-latency networks.

What is the difference between HTTP/3 confirmed and advertised?

Confirmed means a live HTTP/3 handshake over QUIC actually completed in this test. Advertised means your server announced an h3 option in the Alt-Svc header, but this test did not verify that endpoint responds.

What is QUIC and how does it relate to HTTP/3?

QUIC is a transport protocol over UDP that combines connection setup with TLS 1.3 encryption and supports stream multiplexing without head-of-line blocking. HTTP/3 is HTTP mapped onto QUIC, so confirming HTTP/3 means completing a QUIC handshake.

How do clients discover HTTP/3 via Alt-Svc?

A server sends an Alt-Svc response header advertising an h3 endpoint, telling clients they may retry over QUIC. Browsers typically connect first over HTTP/2, read Alt-Svc, then upgrade to HTTP/3 on subsequent requests.

How do I enable HTTP/3 on my server?

Enable QUIC and HTTP/3 in your web server or CDN, allow inbound UDP on port 443 through firewalls, and emit an Alt-Svc header advertising h3. Many sites get HTTP/3 simply by enabling it at their CDN edge.

Why does my site advertise h3 but not confirm HTTP/3 here?

Often UDP 443 is blocked by a firewall, the QUIC listener is misconfigured, or only the edge speaks h3 intermittently. Advertising via Alt-Svc is a promise; a failed QUIC handshake means clients quietly fall back to HTTP/2.

Do I need HTTP/3 if I already have HTTP/2?

Not strictly. HTTP/3 mainly helps users on unreliable or high-latency mobile networks by surviving packet loss and network changes better than TCP. It is a worthwhile enhancement rather than a replacement for a working HTTP/2 setup.

Does HTTP/3 require TLS?

Yes. QUIC integrates TLS 1.3 directly into the transport, so HTTP/3 is always encrypted by design. There is no cleartext HTTP/3, and a valid certificate is required for the handshake this test performs.

Does HTTP/3 make a page faster?

It can reduce connection setup cost or recover better on some networks, but a successful handshake does not prove a faster page. Confirm the effect with repeated field or browser measurements for the audiences you serve.

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