How to Enable HTTP/2 and HTTP/3

Enable HTTP/2 as the compatible baseline and HTTP/3 as an extra improvement where the infrastructure supports it.

Order
the fix

Do it
yourself

Check
manually

Safe modern-protocol configuration

Ask the hosting provider first — HTTP/2 is often included

HTTP/2 and HTTP/3 are configured where the secure connection terminates: hosting, web server, proxy or CDN. The easiest route is the ready-to-use support request below.

Hosting support, TLS, server and CDN configure HTTP/2 and HTTP/3 in sequence — Identify the TLS layer first, then change configuration at that exact layer.

Message for support

Hello,
HTTPS already works for example.com.
Please verify and enable HTTP/2 for the canonical address.
If HTTP/3 (QUIC) is supported, enable it as well
while retaining HTTP/2 for compatibility.
Please confirm the externally available protocols.

Cloudflare or another CDN

Confirm traffic is proxied through the CDN rather than DNS-only.
Find the HTTP/2 and HTTP/3/QUIC network settings.
Keep HTTP/2 enabled and add HTTP/3 where available.
Purge cache only if required and test externally.

Technical notes

Where to find the setting
Layer	Check	Important
TLS	ALPN with `h2`	Working HTTPS is required
HTTP/3	QUIC and UDP 443	Do not disable HTTP/2
Proxy/CDN	Protocol on the public connection	The origin may use another protocol
Web server	Installed-version support	Test config before reload

Do not paste an arbitrary directive

Syntax depends on the Nginx or Apache version, panel and proxy design. Use documentation for the installed version, then test pages, APIs and assets.

Finish with a manual HTTP/2 and HTTP/3 check.

An Automatic check is available at the top of this page. You can independently confirm its result using the manual verification instructions, then fix the issue yourself or order a professional fix.