Resolved http2 not working + downgrade to http/1.1

[Daniel Slyman]

Dear fellow Pleskians,

I would like to inform you of an issue I came across, one which had cost me many many hours in an unforgiving search for the solution to my issue:

For whatever reason, on a fresh install of Plesk, one single website was being served with http2 while the rest was being served by http/1.1. I tried every solution on the Plesk KB and Forum, no luck.

So before you go on a wild witch hunt, if you are using some kind of AdBlocker which monitors your HTTP traffic on your local machine, try disabling it. Sounds obvious, I know, but I've been using AdGuard for several years now and never thought about it again. (The one website was being served by h2 because of some rule I must have set ages ago and wasn't aware of anymore, in case you were wondering).

Hopefully this will help someone, someday, somewhere.

Greetings,
Daniel

 

[Dukemaster]

Hi Daniel,
I'm interested in your issue. Would be nice if you could show a lil more informations about it. For example which single site was working and which ones not. Perhaps a few details of the tests you made and the results you get in your console. I mean how you made the test and which support articles you tried without success.
I have 8 domains on my server and all have http2 with ALPN enabled.
Greets

 

[Daniel Slyman]

Hey there,

as I mentioned, it was a local issue to do with AdGuard, my seemingly very intrusive AdBlocker which sits between you and your browser traffic. For some reason it downgrades the h2 connection to a http/1.1 connection. Interestingly the connection is still multiplexed, so it might just be a cosmetic issue in the browser network console. I don't have any articles to support my claim, only anecdotal evidence I chose to share here since other people had the same issue but with different causes. Hence, I am sharing this in order to save someone else the pain of sifting through alternative solutions when it could just be that you're using AdGuard or something similar.

The 'one' site that was working, was a client's website and it seems I created an exclusion rule a long time ago when I was building the website, probably because some social sharing buttons weren't being displayed.

As for the testing procedure, you can just open the browser developer console, hit the network tab, make 'protocol' visible and there you see which protocol is being used. Thus, http/1.1 or h2. There are plenty of guides online showing you how to do this.

Are you having issues?