Mozilla has announced that after nine years of work, they have finally deleted the latest components of the Firefox code that were formed using the space of the names XUL. This means that ordinary web technologies, mainly CSS Flexbox, and not specific XUL-Box, -Moz-INLINE-BOX, -Moz-Grid, Moz-Stack, -Moz-Popup, are now used to draw the Firefox user interface. However, Xul is still being used as an exception to display the system menu and pop-up panels.
The possibility of using XUL in additions was discontinued in 2017, and the interface was spared the links in the language xbl in 2019. Meanwhile, the Xul-developers continued to be formed applied when forming the elements of the elements Browser interface. XBL prisoners that determine the behavior of the XUL-video were replaced by web components.
Looking ahead to the future, Mozilla plans to use the API Popover for the functionality provided by Xul. By taking these steps, Mozilla is making the Firefox user interface easier to maintain and simpler to develop while still maintaining its unique look and feel.