Configure HTTP/2 on Apache

HTTP/2 is an update to the original Hypertext Transfer Protocol (HTTP) specification offering improvements in efficiency and latency. The new version, which adds several useful features, is compatible with browsers that only support HTTP/1. HTTP/2 has many advantages and no significant drawbacks, so upgrading to the new version is recommended. This guide explains how to configure and use HTTP/2 on an Apache server and how to test it is working.

Understanding HTTP/2

HTTP/2 is supported by the majority of the most popular websites and is considered the current standard. It dramatically improves speed and latency due to optimizations in how data is transmitted. However, most of the changes are internal, and users do not have to make any adjustments. HTTP/2 still uses the same fields, format, and status codes, and serves the same function as the original HTTP service. It continues to use Transmission Control Protocol (TCP) for the transport layer and supports all contemporary browsers, web servers, and proxies. A negotiation mechanism helps the client and server elect whether to use HTTP/2 or fall back to HTTP/1.1. Most clients require data encryption whenever HTTP/2 is used. This means HTTPS is the de facto standard in HTTP/2.

For more comprehensive information and a collection of resources about HTTP/2, see our An Introduction to HTTP/2 guide.

Before You Begin

1. If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.

2. Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.

3. Ensure you possess a Fully Qualified Domain Name (FQDN) for the website. The DNS records for the site must point to the Linode server.

Note

The steps in this guide are written for non-root users. Commands that require elevated privileges are prefixed with sudo. If you are not familiar with the sudo command, see the Linux Users and Groups guide.

A Summary of the HTTP/2 on Apache Configuration Process

The following high-level steps are involved in configuring HTTP/2 on Apache. The commands in this guide work on Ubuntu systems, but are generally applicable to all Linux distributions.

1. Install Apache
2. Install the Necessary PHP Components
3. Configure Apache to Support HTTP/2
4. Enable HTTPS Support

Install Apache

Run the apache2 -v command to determine whether Apache is installed. If it is already present, the command indicates what version is running. In this case, skip this section and proceed to the Install the Necessary PHP Components step. If the command displays an error, Apache is not yet installed. For more information about Apache, see Linode’s Apache Configuration Basics guide.

Note

HTTP/2 support requires Apache version 2.4.17 or higher.

1. Update the system packages. Reboot the system if advised to do so.

    sudo apt-get update
    sudo apt-get upgrade
   

2. Install the apache2 package.

    sudo apt install apache2
   

3. Verify Apache is active using systemctl.

    systemctl status apache2
   

   apache2.service - The Apache HTTP Server
        Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
        Active: active (running) since Tue 2021-05-04 13:01:06 UTC; 50s ago

4. (Optional) To configure Apache so it does not launch automatically whenever the server reboots, disable the entry in systemctl. To configure it to activate on reboot again, use the systemctl enable command.

    systemctl disable apache2
   

5. Configure the ufw firewall to enhance security. Allow ufw to accept OpenSSH and Apache Full connections. Apache Full allows both HTTP and HTTPS requests through.

    sudo ufw allow OpenSSH
    sudo ufw allow 'Apache Full'
   

6. Enable ufw.

    sudo ufw enable
   

7. Confirm the webserver is working. Type the address of the Linode server into the address bar of the browser. If Apache is working properly, the browser displays the default Apache landing page. The connection is still using HTTP/1.1 at this point.

Install the Necessary PHP Components

To properly configure Apache, you need to upgrade some of your system’s php modules so they are compatible with HTTP/2.

1. Install the php7.4-fpm module. Disable the older version of this module and enable the new one.

    sudo apt-get install php7.4-fpm
    sudo a2dismod php7.4
    sudo a2enconf php7.4-fpm
   

   Note

   If PHP was not previously installed, the message ERROR: Module php7.4 does not exist! is displayed when php7.4 is disabled. You can ignore this message.

2. Enable the proxy_fcgi module.

    sudo a2enmod proxy_fcgi
   

Configure Apache to Support HTTP/2

To enable HTTP/2 support, enable some additional modules and configure the virtual server to allow the protocol.

1. Disable the mpm_prefork module, which is not compatible with HTTP/2. This module might already be disabled.

    sudo a2dismod mpm_prefork
   

2. Enable the mpm_event module.

    sudo a2enmod mpm_event
   

3. Enable the ssl module.

    sudo a2enmod ssl
   

4. Enable the http2 module to activate HTTP/2 support.

    sudo a2enmod http2
   

5. Restart Apache to apply all the changes.

    sudo systemctl restart apache2
   

6. Verify Apache is still active using the systemctl status command.

    systemctl status apache2
   

7. Locate the .conf file that contains the Protocols definition. Depending on the installation, this is either found at /etc/apache2/apache2.conf or /etc/apache2/mods-available/http2.conf. To find the exact file, change to the root directory for Apache and search for the “Protocols” keyword with the grep command. Select the file that already contains a “Protocols” configuration. If there are no matches, choose the base apache2.conf file.

    cd /etc/apache2
    grep -r Protocols .
   

   Note

   Earlier versions of Apache have a different file and directory structure. The main Apache .conf file might be located at /etc/httpd/httpd.conf, /etc/httpd/conf/httpd.conf, or /usr/local/apache2/apache2.conf.

8. Edit this file and add the h2 and h2c protocols to the “Protocols” definition. Apache tries to negotiate the protocols in the order they are listed. Placing h2 first prioritizes HTTP/2 over HTTP/1.1.

   File: /etc/apache2/mods-available/http2.conf

   1 2 3 4

   ... Protocols h2 h2c http/1.1 ...

   Note

   HTTP/2 support is typically configured on a system-wide basis. If you only want to enable HTTP/2 for one site, add the h2 h2c protocols to the virtual server entry for the site instead. For more information about Apache, see Linode’s Apache Configuration Basics guide.

Enable HTTPS Support

Most clients only support HTTP/2 if encryption is enabled, so HTTPS must be enabled to use it. HTTPS allows for website authentication and ensures all data is transmitted privately. To accept HTTPS requests, a website must possess a public key certificate signed by a trusted certificate authority. This certificate ensures the owner operates the website in question.

Let’s Encrypt allows website owners to easily generate certificates. The Certbot tool automates the entire certificate-granting operation. It identifies all of the relevant domains and manages the challenge requests and the granting process. It also makes all necessary changes to the Apache configuration.

Install Certbot using the snap utility. Snap is pre-installed on Ubuntu.

1. Run the following commands to update Snap. Verify the current version.

    sudo snap install core
    sudo snap refresh core
    snap version
   

   Note

   If Snap is not already installed, install it using the command sudo apt install snapd.

2. Remove any existing Certbot packages to avoid possible conflicts.

    sudo apt-get remove certbot
   

3. Install Certbot.

    sudo snap install --classic certbot
   

   The Snap module confirms Certbot is installed.

   certbot 1.12.0 from Certbot Project (certbot-eff) installed

4. Configure a symbolic link to the Certbot directory.

    sudo ln -s /snap/bin/certbot /usr/bin/certbot
   

5. Run Certbot to generate certificates for each domain. You can create multiple certificates with one command by specifying the -d option in front of each domain. Substitute your own domain name in place of example.com throughout the following section.

    sudo certbot --apache -d example.com -d www.example.com
   

   Certbot displays updates about the requests and challenges and then confirms the domains are successfully enabled. You might be required to supply some additional information if you have never used Certbot before.

   Requesting a certificate for example.com and www.example.com
   ...
   Deploying Certificate to VirtualHost /etc/apache2/sites-enabled/example.com-le-ssl.conf
   Deploying Certificate to VirtualHost /etc/apache2/sites-enabled/example.com-le-ssl.conf
   
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Congratulations! You have successfully enabled <https://example.com> and
   <https://www.example.com>
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   ...

6. Restart Apache to apply the changes.

    sudo systemctl restart apache2
   

Verify HTTP/2 Support is Enabled on Apache

To confirm Apache is using HTTP/2, visit the website using any browser, and use the developer tools to inspect the incoming packets. The following instructions demonstrate this technique on Firefox. Each browser has its own method of inspecting incoming packets. Consult the browser’s documentation for more details.

1. Visit the domain using Firefox.

2. Open the Firefox Developer Tools. Select Tools followed by Browser Tools and then Web Developer Tools. This opens a new panel at the bottom of the browser.

3. Select the Network tab, and reload the page again.

4. This displays a list of several rows. Click on the row corresponding to the base domain. This reveals a new panel on the bottom right. The Headers tab appears by default.

   

5. If HTTP/2 is working, the Status reads OK and the version is HTTP/2.