How to enable HTTP/2 protocol support in Apache

HTTP/2 is an updated version of HyperText Transfer Protocol that improves web performance through multiplexing, header compression, and more efficient data transfers. It reduces latency and enhances page load speeds, resulting in quicker response times for end users. Support for modern encryption, such as TLS with ALPN, ensures secure and optimized communication between client and server.

Enabling HTTP/2 in Apache requires the mod_http2 module, introduced in version 2.4.17, along with compatible system dependencies and potential updates to OpenSSL for encrypted connections. Loading the correct modules and enabling them in the server configuration allows Apache to handle both plain and secure HTTP/2 traffic, identified by h2c and h2 protocols, respectively. Proper version checks and module loading ensure compliance with modern security standards and the best possible performance.

Configuration changes involve updating Apache directives to accommodate multiplexed streams and advanced flow control. Administrators can set up the server to accept HTTP/2 requests while still serving legacy HTTP/1.1 connections. Verifying these settings is critical for maintaining a performant and stable hosting environment.

1. Launch terminal.
2. Verify that your server is running Apache version 2.4.17 or newer.

   $ apachectl -v
   Server version: Apache/2.4.46 (Unix)
   Server built: Jul 1 2020 09:13:15

   This command outputs the version of your Apache server. Ensure it's 2.4.17 or newer.

   Use httpd -v if you're using CentOS or other Red hat variants.

3. 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

4. Open the configuration file for your Apache website using your preferred text editor.

   $ sudo vi /etc/apache2/sites-available/000-mysite.conf

   Related: Location for Apache VirtualHost configuration

5. 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: Configuration options for HTTP/2

6. Restart Apache to apply the changes.

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

   Related: How to manage the Apache web server service

7. Check that HTTP/2 is enabled by examining the server response headers.

   $ 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