Overview: Early on in the project we decided to use Google Chrome as the default browser, but it was never the intension that FOLIO should not be supporting other of the primary browsers, e.g. Mozilla Firefox, Opera, Safari and Microsoft Edge.
Web Content Accessibility Guidelines (WCAG) 2.1, an accessibility standard required by law in the European Union and many other countries, requires in its section 4:
Content must be robust enough that it can be interpreted by by a wide variety of user agents, including assistive technologies.
Guideline 4.1 Compatible
Maximize compatibility with current and future user agents, including assistive technologies.
Browsers are user agents. Supporting all primary browsers makes it more likely that we support a browser that works with the assistive technology (like braille display) the user needs.
Cross-browser compatibility is state of the art and is supported by most frameworks and software libraries, it requires little effort. Not supporting the primary browsers puts libraries at risk of being sued for violating the disability act.
Status as of Juniper 2021:
FOLIO supports only Chrome. And in this context the "Support" means that the FOLIO project is obligated to fix rendering bugs for Chrome browser only. As of right now, if rendering bug found in Fire Fox, Safari or any other browser we don't have to fix it - Jiras are closed as "Won't Do": https://issues.folio.org/issues/?jql=(text%20~%20firefox%20OR%20text%20~%20safari)%20AND%20resolution%3D%22Won%27t%20Do%22%20