Apache is a free and open-source cross-platform web server software.
Header Footer Code Manager by Draftpress is a easy interface to add snippets to the header or footer or above or below the content of your page.
Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Open Graph is a protocol that is used to integrate any web page into the social graph.
PHP is a general-purpose scripting language used for web development.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.
WordPress Super Cache is a static caching plugin for WordPress.
Yoast SEO is a search engine optimisation plugin for WordPress and other platforms.