Icons
Bootstrap icon:
Free, high quality, open source icon library with over 1,800 icons. Bootstrap Icons are published to npm, but they can also be manually downloaded if needed. Include the icon fonts stylesheet—in your website < head> or via @import in CSS—from jsDelivr and get started in seconds.
Can visit the site for more reference https://icons.getbootstrap.com/
Font Awesome Icons:
An open source icons library with support to multiple stacks like, react.js, vue.js, angular, Python/Django, wordpress, Less, Ember & SCSS.
Can visit the site for more reference https://fontawesome.com/icons
Iconic Icons
Premium designed icons for use in web, iOS, Android, and desktop apps. Support for SVG and web font. Completely open source, MIT licensed and built by Ionic
Can visit the site for more reference https://ionic.io/ionicons