HTTP/3 (QUIC) not detectable in Chrome Canary with --enable-quic --quic-version=h3-23

Cloudflare activated HTTP/3 (QUIC) on one of my domains.

I have enabled HTTP/3 (QUIC) for the domain

Downloaded Chrome Canary browser for Win 10 64 bit.

Added the following in the target field (by accessing Chrome Canary.exe properties)
“C:\Users\Name\AppData\Local\Google\Chrome SxS\Application\chrome.exe” --enable-quic --quic-version=h3-23

Enabled the support for HTTP/3 (QUIC) in Chrome://flags/

Visited the website and looked at the developer tools > network tap > protocol > it is mostly h2 or http/1.1 for all resources except Google resources which are http/2+quic/46

Tried for too and no luck.

No http/2+quic/46, only h2 or http/1.1


Note that due to how HTTP/3 is negotiated between the browser and the server, HTTP/3 might not be used for the first few connections to the domain, so you should try to reload the page a few times.

Actually I reloaded over 50 times.

i didn’t have to do that step for it to work, so maybe reverse that

Wasn’t able to get it on, but got it on my own first try (but not on the first request due to how H3 negotiates itself as said above)

Yeah, I have set it to ‘default’ but still the same result. I’m wondering why.

Try canary browser with http/3 flags enabled --enable-quic --quic-version=h3-23 on other cloudflare http/3 enabled sites to verify it isn’t a problem with your browser/pc

The browser doesn’t seem to show http/2+quic/46 for all the websites listed above.

Both in Incognito mode and normal mode of Chrome Canary

(with “C:\Users\Name\AppData\Local\Google\Chrome SxS\Application\chrome.exe” --enable-quic --quic-version=h3-23) on target field of Chrome Canary.exe properties.

yeah could be Chrome canary related as it’s still experimental and needs development over time

custom built curl with HTTP/3 support verifies HTTP/3 h3-23 draft though

curl-http3 --http3 -4Iv
*   Trying
* Sent QUIC client Initial, ALPN: h3-23
* h3 [:method: HEAD]
* h3 [:path: /]
* h3 [:scheme: https]
* h3 [:authority:]
* h3 [user-agent: curl/7.67.0-DEV]
* h3 [accept: */*]
* Using HTTP/3 Stream ID: 0 (easy handle 0x55ee8a4a1e60)
> Host:
> user-agent: curl/7.67.0-DEV
> accept: */*
< HTTP/3 200
HTTP/3 200
< date: Sat, 28 Sep 2019 11:31:03 GMT
date: Sat, 28 Sep 2019 11:31:03 GMT
< content-type: text/html
content-type: text/html
< content-length: 106072
content-length: 106072
* Added cookie __cfduid="d079b09c43b049741d413eec8c12cea2e1569670263" for domain, path /, expire 1601206263
< set-cookie: __cfduid=d079b09c43b049741d413eec8c12cea2e1569670263; expires=Sun, 27-Sep-20 11:31:03 GMT; path=/;; HttpOnly; Secure
set-cookie: __cfduid=d079b09c43b049741d413eec8c12cea2e1569670263; expires=Sun, 27-Sep-20 11:31:03 GMT; path=/;; HttpOnly; Secure
< alt-svc: h3-23=":443"; ma=86400
alt-svc: h3-23=":443"; ma=86400
< expect-ct: max-age=604800, report-uri=""
expect-ct: max-age=604800, report-uri=""
< server: cloudflare
server: cloudflare
< cf-ray: 51d5638c0cf2c5e4-EWR
cf-ray: 51d5638c0cf2c5e4-EWR
* Connection #0 to host left intact

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