Safari 14 HTTP/3 support


Today i upgraded to safari 14. How to identify if it is using http/3 or not?

Partial support in Safari refers to being limited to macOS 11 Big Sur and later.

Not available on iOS.

iOS 14 also has HTTP/3 support.

See /cdn-cgi/trace

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It’s interesting that Can I Use shows MacOS Safari 14 as supporting it, but iOS Safari 14 says not supported by default, but can be enabled. Enabled how?

Ah, Settings -> Advanced -> Experimental Features.


Interestingly I’m getting CAPTCHA errors (Google’s) which might be HTTP/3 related. Intermittent, but specific to my iPhone and not other devices in the same network, nor does VPN to elsewhere help.

I’m still investigating, it is possible I have another experimental feature enabled too.

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so u guys able to run http/3?

Yes, for a few beta releases now. And on the iOS public release.

I has safari 14 (full version), tried with http/3 enable from cloudflare. site got served with http/2 only.

Even the above mentioned example showing http/2
uag=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0 Safari/605.1.15

Did you enable HTTP/3 in Safari settings on iOS? It’s in Settings -> Safari -> Advanced -> Experimental -> Toggle “HTTP/3”

Then I had to close Safari (kill it), and re-open it, and I was able to see http=http/3 when I visited

I also saw http=http/3 when I visited your site

I am testing on mac os not on ios. There is no option in experimental feature for http/3.

No such option for http/3 here.

What version of MacOS and Safari are you testing with?

Safari - Version 14.0 (15610., 15610)
Macos - 10.15.6 (Catalina)

As said above it’s limited to only macOS 11 Big Sur.

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Wasn’t there a company where everybody complained about the deep integration of their browser into their operating system? :wink:

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  • HTTP/3 in Safari 14 is currently partially broken, at least when used in conjunction with Cloudflare: Cloudflare Access broken on iOS 14
  • HTTP/3 is currently unavailable on macOS Catalina, even if you’re using Safari 14.
  • If you’ve upgraded to the latest version of iOS, HTTP/3 may or may not be enabled on your device. I’d recommend leaving it disabled for now, seeing how it’s still quite buggy. If you want to forcefully toggle it, there’s an “experimental features” menu in Settings -> Safari. You’ll need to force-quite Safari after changing the settings there before they will take effect.
  • To check whether your device is using HTTP/3, visit and look at the http field.

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