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I have been searching the web but I can't find any test to see if the browser I'm using is currently supporting HTTP/3 and if it is enabled. The websites I find are only for testing if websites support HTTP/3. Is there any website for testing if a browser supports HTTP/3?

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    Note that if you're behind a proxy, as I am, the tests given in the answer will be testing whether the proxy supports HTTP/3. You could get a false positive -- test site reports success because proxy supports it when your browser doesn't -- or you could get a false negative -- test site reports failure because proxy doesn't support it even though browser does. Jul 26, 2021 at 15:47

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cloudflare-quic.com

Cloudflare offers a HTTP/3 test at cloudflare-quic.com. I had to reload the page for it to work.

This is what it looks like for me after a reload (with HTTP/3 supported):

Successful test at cloudflare-quic.com

quic.nginx.org

You can test if your browser supports HTTP/3 at quic.nginx.org which is hosted by NGINX. The test doesn't usually require a page reload.

This is what it looks like for me:

Successful test at quic.nginx.org

http3.is

You can also use http3.is by Fastly, but it might also require a page reload before it works.

This is what http3.is looks like for me (with HTTP/3 supported):

Successful test at http3.is

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    Why is reloading necessary?
    – Pedro A
    Jul 26, 2021 at 13:54
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    @PedroA because the Alt-Svc mechanism works kind of like HSTS. The browser makes an initial request using HTTP2, and the response to that request includes a header telling the browser that it can try HTTP3 for that domain in the future.
    – hobbs
    Jul 26, 2021 at 14:14
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    The http3.is website is the least reliable, the other ones required 1 reload in oder to work, but the http3.is website keeps saying my browser does not support http3
    – Ferrybig
    Jul 27, 2021 at 14:52
  • @Ferrybig I've been having some issues with quic.nginx.org lately as well so I've changed the order. Feb 2 at 21:22

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