Can I Disable HTTP/2?

Yes. HTTP/2 is enabled by default for SSL listeners, but may be turned off at the virtual host level with the SpdyEnabled directive in the httpd.conf configuration file, or via the WebAdmin Console.

In httpd.conf, use the SpdyEnabled off directive to disable all protocols, like so:

<IfModule LiteSpeed>
SpdyEnabled off
</IfModule>

Other valid parameters are spdy2, spdy3, http2, and http3.

NOTE: All protocols (except the SPDY protocol, as of v6.0.12) are enabled by default. When you use this directive to explicitly enable one or more protocols, anything not selected will be disabled. So, if you wanted to disable HTTP/2, but you still wanted to keep HTTP/3 enabled, you would have to use SpdyEnabled http3. This would enable HTTP/3 while leaving everything else (including HTTP/2) off.

In the WebAdmin Console, you can find the Enable SPDY/HTTP2/HTTP3 option in the SSL tab for both Listeners and Virtual Hosts. Deselect the HTTP/2 option to disable HTTP/2.

IMPORTANT: You CANNOT modify your virtual host configuration directly when using a hosting control panel as the changes may be overwritten whenever the hosting control panel regenerates the Apache configuration file. You can find more information on virtual host include files for your specific control panel here: cPanel, Plesk, DirectAdmin