Why Did Mozilla Remove XUL Add-ons?
TL;DR: Firefox used to have a great extension mechanism based on the XUL and XPCOM. This mechanism served us well for a long time. However, it came at an ever-growing cost in terms of maintenance for both Firefox developers and add-on developers. On one side, this growing cost progressively killed any effort to make Firefox secure, fast or to try new things. On the other side, this growing cost progressively killed the community of add-on developers. Eventually, after spending years trying to pr...
Source: yoric.github.io