Errors / Network errors

net::ERR_QUIC_PROTOCOL_ERROR

The fast connection mode Chrome tried with the server (HTTP/3) failed.

The request fails, where HTTP/2 would have worked.

Why it happens

A network that blocks or mangles UDP, which HTTP/3 uses: corporate firewalls, some VPNs.
A server or CDN whose HTTP/3 support is misconfigured or partly rolled out.

How to fix it

If it fails for everyone, check or turn off HTTP/3 at the CDN; Chrome falls back to HTTP/2 when it is not offered.
If only some visitors see it, it is their network.
To confirm, open chrome://flags, disable Experimental QUIC protocol, and reload: if the page works, HTTP/3 is the cause. DevTools' Network panel, with the Protocol column shown, says h3 for requests that used it. A CDN setting that turns HTTP/3 off is usually one switch, and nothing else about the site changes.

Whose problem it is

Either the site's own code or a third party's, depending on where it comes from.

Does your site have it?

Free, no account. We open your page and four more in a clean Chrome and list every error like this one, with the page and the click that caused it. How the free page check works.

Often seen with

ERR_HTTP2_PROTOCOL_ERRORThe server broke the rules of the connection while sending its answer.