How to enable HTTP/2 for Apache

HTTP/2 is a major improvement over HTTP/1.1 especially in the speed department. HTTP/2 is supported by Apache though it's not enabled by default.

HTTP/2 could simply be enabled on Apache by installing required module and configure Apache to serve requests using HTTP/2 instead of the default HTTP/1.1

1. Launch terminal application.
2. Enable http2 module for Apache.

   $ sudo a2enmod http2 # Ubuntu, Debian and SUSE
   Enabling module http2.
   To activate the new configuration, you need to run:
     systemctl restart apache2

   • Distribution with a2enmod support can simply run the command above without having to manually enable the required modules.
   • Fedora, CentOS and Red Hat enables the module by default so requires no manual action to enable the modules.

   Related: How to enable or disable Apache modules

   Options	Debian, Ubuntu	openSUSE and SLES	Fedora Core, CentOS, RHEL	macOS	homebrew	xampp
   a2enmod support	yes	yes	no	no	no	no
   Modules to install	none
   Module name	n/a			http2
   Loadmodule directive	n/a			LoadModule http2_module <module_locations>/mod_http2.so

3. Add relevant Protocols directive in main Apache configuration file or on a specific virtual server configuration.

   <VirtualHost *:80>
           # .....
           # ....
           Protocols h2 h2c http/1.1
   </VirtualHost>

   Related: Location for Apache VirtualHost configuration

   Related: Configuration options for HTTP/2

4. Restart Apache service for the changes to take effect.

   $ sudo systemctl restart apache2 # Ubuntu and Debian
   $ sudo systemctl restart httpd # CentOS and Red Hat

   Related: How to start, restart and stop Apache service

5. Test by accessing the service using curl.

   $ curl --http2 --head  www.simplified.guide
   HTTP/1.1 101 Switching Protocols
   Upgrade: h2c
   Connection: Upgrade
   
   HTTP/2 200
   date: Sun, 00 Jan 1900 00:00:00 GMT
   server: Apache/2.4.41 (Ubuntu)
   last-modified: Sat, 08 Feb 2020 14:15:13 GMT
   etag: W/"2aa6-59e11227347f6"
   accept-ranges: bytes
   content-length: 10918
   vary: Accept-Encoding
   content-type: text/html