LiteSpeed Web Server supports HTTP/2 out of the box since the introduction of Enterprise Version 5.0. HTTP/2 is enabled by default for the SSL listeners configured in httpd.conf and Web GUI. HTTP/2 can be customized via “SpdyEnabled” directive.

SPDY is also enabled by default since the introduction of Enterprise Version 5.0. However, if using a front-end SSL proxy server, enabling SPDY or HTTP/2 on LiteSpeed Web Server will have no effect, as front-end SSL proxies are not capable of forwarding SPDY and HTTP/2 requests.

Please note, HTTP/2 requires OpenSSL 1.0.2 as minimum. OpenSSL versions less than 1.0.2 will force HTTP/2 connections to HTTP/1. However, LiteSpeed Enterprise Web Server is staticly linked with latest OpenSSL 1.0.2 release and it does not depends on the OpenSSL version coming with the system.

HTTP/2 should work out of box for all HTTPS sites with LiteSpeed.

Although HTTP/2 specification does not require TLS, TLS is required by browser implementations.

Though you can use the third party web tools to check, the most common and easy way to check is through browser's developer tools. h2 and http/2 mean HTTP/2 has been enabled for your server.

If you use third-party web tools, it could show as the following: