Http/3 over CF doesent work

Hello, my website use quic http/3 and it work ok when im not over proxy CF, but when i switch to CF my website doesent use http/3 protocol over udp 443. Does anyone know why? Regards


Seems to work just fine on

it work when u test but when u load over CF it load over H2

and external resources load fine http2+ quic (microsoft edge) and over chrome:

but when i disable CF it load whole domain to http3

That might be an issue with Chrome.

Firefox loads it just fine on HTTP 3


Keep in mind HTTP 3 is still very much in development.

so problem is chrome over cloudflare?

It might be that Chrome does not support that particular flavour yet. Maybe make sure you have the latest development build of Chrome.

Generally speaking, your site is reachable on HTTP 3 just fine.

yah u are right. over firefox all resoruce except cloudflare rocket loader go over http3

1 more thing as u can see here this is test whitout cloudflare

and with cloudflare

as u can see here cf missing even new chrome protocol and some more…

Your server seems to support more flavours of HTTP 3 than Cloudflare’s proxies.

HTTP 3 is relatively messy at this point and - as mentioned before - mostly still under development. I would not focus too much on that. HTTP 1 still works great, HTTP 2 is relatively stable too, and HTTP 3 will be usable in the foreseeable future as well.

Also make sure you have configured Chrome correctly according to

Overall I’d recommend Firefox as the implementation seems to be more advanced and easier to enable.

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note Google QUIC and HTTP/3 over QUIC are not the same - Cloudflare supports HTTP/3 via draft 27-29 (H3-27 to H3-29) it doesn’t support Google QUIC (QUIC/43 and QUIC/46)

HTTP/3 is only supported in Google Canary dev browser via flags either one of these flags and not regular Google Chrome

  • --enable-quic --quic-version=h3-27
  • --enable-quic --quic-version=h3-28
  • --enable-quic --quic-version=h3-29

Google Canary with the flag --enable-quic --quic-version=h3-29


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