How can I tell if HTTP/2 or SPDY is working for my website?

Note: HTTP/2 and SPDY are not used for the connections between Cloudflare and the Origin server. Read more here.

When a client makes a connection to your website both  the web browser and server will automatically use the highest protocol available. This means that HTTP/2 takes precedence over SPDY, and SPDY takes precedence over HTTP/1.x.

How CloudFlare HTTP/2 Works

To determine what protocol is used for your connection you can visit [example.com]/cdn-cgi/trace (replacing [example.com] with your domain name). You should see information similar to the example below:

fl=21f63
h=www.cloudflare.com
ip=108.61.197.168
ts=1420194924.494
visit_scheme=http
uag=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36
colo=SJC
http=h2
loc=US

The line http=h2 in the above example indicates that HTTP/2 is being used. Other possible values are http=spdy/3.1 for SPDY/3.1 and http=http/1.x for HTTP/1.x.

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