Font Awesome 4
If you use HTML or CSS syntax, Iconify loads icons from Iconify API. To use Iconify without relying on Iconify API there is possibility to host custom API and bundle icons with custom scripts or use Iconify for React.
There are no native components yet for frameworks except React.
Additionally integration is being developed for XenForo 2 forum software. It features icon picker component that includes icon search, custom option and style property types, custom XenForo template tags, making it easy to add icon pickers to third party styles and add-ons.