Icons

Google Icons

Google icons in iOS, Material, Windows, and other design styles

Bootstrap 3 Glyphicons

Includes over 250 glyphs in font format from the Glyphicon Halflings set. Glyphicons Halflings are normally not available for free, but their creator has made them available for Bootstrap free of cost.

Font Awesome 4 Icons

You place Font Awesome icons by using the prefix fa and the icon's name.

Font Awesome 5 Icons

Font Awesome 5 has a PRO edition with 7842 icons, and a FREE edition with 1588 icons. This tutorial will concentrate on the FREE edition.