Created attachment 465619 [details] Chrome dev tools showing h3 protocol vs Safari showing blank Steps - Use Safari Version 16.4 (18615.1.26.11.22). Running on M2 MacBook air. - Visit www.jetblue.com which, according to https://http3check.net/?host=www.jetblue.com, has QUIC & HTTP/3 supported. - inspect page - switch to network tab - Right click table column headings and ensure "Protocol" is visible. - Refresh the page Observe that there's no network calls labeled as "H3". background: It's my understanding that Safari 16.4 has enabled Http/3 by default as per https://bugs.webkit.org/show_bug.cgi?id=251952 Though https://caniuse.com/http3 still has it marked as "not supported by default" I'm a product owner so not as technical but it's my understanding that engineers on my team have enabled http3 on our infustructure and our services should be making requests with it. When we looked at Google Chrome inspect tools to validate, we could see that some network calls switch from h2 protocol to many h3. But in Safari I don't see that. I know that first connections are on http/2 but on refresh a few times I'd expect to see H3. see attached comparison of Chrome protocols vs safari 16.4
I do see some "h3" when I shift-reload the page. I think that these steps demonstrate that all HTTP/3 resources happen to be cached, and get loaded from memory cache on regular reload. I also see h3 on http3check.net itself.
OK, may be I'm just getting most things via the CDN on Safari. I wanted to feel confident that Http3 was supported in Safari now, which I wasn't because it wasn't in release notes I saw, not on caniuse.com (I'm sure they'll catch up), and I wasn't seeing it in the network panel. Surprised there's not more hype for this since on mobile it will really help with lost packets. we just upgraded a few other parts of our services to http3 today so it was a happy coincidence 16.4 also launched. But I didn't want to tell other folks because I wasn't sure it actually was supported. Thanks for your time. I'll let the engineers on my team know they can start testing it.