Apache is a free and open-source cross-platform web server software.
Drupal is a free and open-source web content management framework.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Popper is a positioning engine, its purpose is to calculate the position of an element to make it possible to position it near a given reference element.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.