Failed to load resource: net::ERR_HTTP2_PROTOCOL_ERROR

Hi,
we see a lot of aborts when Users try to visit one of our shops.The Chrome console shows
Failed to load resource: net::ERR_HTTP2_PROTOCOL_ERROR

The other shop on the same server and dns controlled by cloudflare too, works fine.

The problem occurred for the first time 01/31/2024 - 10:51 a.m. (UTC/GMT +1, Berlin).

Hi there,

Sorry for the issues you are facing.

A ERR_HTTP2_PROTOCOL_ERROR historically from my experience has been caused by a malformed HTTP response header on the origin server - the way that chrome specifically enforces correct syntax of HTTP response headers over HTTP/2 causes this error when a header is not formatted correctly.

You should make a request directly to your origin server and take a look at the HTTP response headers and see if you can see anything that looks abnormal.

Normally what I’ve seen in the past is content-security policies being formatted over multiple lines instead of a single line etc.

You can use curl if you are familiar

curl -svo /dev/null https://example.com --connect-to ::<origin_IP>

Replacing the <origin_IP> with the IP address of your web server to see what headers are being returned from your web server.

Hope this helps!