HTTP/2 (also known as HTTP/2.0 and HTTP 2.0) is the second major version of the HTTP network protocol used by the World Wide Web. Ratified in May 2015, HTTP/2 was created to address some significant performance problems with HTTP 1.1. The advantages of this protocol can be found here. Currently HTTP/2 is supported by most major web browsers.
Note: HTTP/2 is supported for SSL sites only, so non-SSL sites will continue to work under HTTP/1.x.
How to Enable HTTP/2 support for your web site
Make sure you have Nginx webserver updated to the latest version and running. You can do this on the Tools & Settings -> Server Components and the Tools & Settings -> Services Management pages.
Login to your server via SSH under root and enable HTTP/2 support in Plesk using the following command-line utility:
# plesk bin http2_pref enable
During the last step, your Nginx web server will be tuned to use the TLS protocol with modern and secure ciphers, the whole web server configuration will be rebuilt, and all your and your customers’ web sites with SSL support will be moved to HTTP/2.
Note: You can simply use an online service like https://tools.keycdn.com/http2-test to check that HTTP/2 is enabled on a domain.
If you wish to return to HTTP 1.x and to disable HTTP/2, please use the following command:
# plesk bin http2_pref disable
ALPN support
For the correct use of HTTP/2 in Google Chrome, Nginx web server has to support the ALPN (Application-Layer Protocol Negotiation). For details, see the ALPN documentation. ALPN support for Nginx web server is available in Plesk for the following operating systems: CentOS 7, RedHat Enterprise Linux 7, Ubuntu 14.04, Ubuntu 16.04, and Debian 8.
This means that HTTP/2 powered by Plesk works on the mentioned operation systems in all modern browsers.
