Icons

Bootstrap 3 shipped with Glyphicons—a nice collection of over 250 font icons, free of use. While great in theory, font icons come with a number of problems in practice:

• Font icons may break screenreaders as the readers will literally try to read out the icon.
• Persons with fonts to aid their reading. Font icons will break if that happens.
• If the icons fail, then the web browser replaces them with a default fallback. This makes controls using these icons look funny at best.

These three major problems, combined with the desire to make Bootstrap 4 more lightweight, led to the development team’s decision to no longer make Glyphicons available (however, this does not prevent one from including font icon set manually).