From the Firefox announcement: Re: Why they are removing XUL: "XPCOM and XUL are two of the most fundamental technologies to Firefox. The ability to write muc

From the Firefox announcement: Re: Why they are removing XUL: "XPCOM and XUL are two of the most fundamental technologies to Firefox. The ability to write much of the browser in JavaScript has been a huge advantage for Mozilla. It also makes Firefox far more customizable than other browsers. However, the add-on model that arose naturally from these technologies is extremely permissive. Add-ons have complete access to Firefox’s internal implementation. This lack of modularity leads to many problems. A permissive add-on model means that we have limited flexibility in changing the foundations of Firefox. ... "The tight coupling between the browser and its add-ons also creates shorter-term problems for Firefox development. It’s not uncommon for Firefox development to be delayed because of broken add-ons. In the most extreme cases, changes to the formatting of a method in Firefox can trigger problems caused by add-ons that modify our code via regular expressions. Add-ons can also cause Firefox to crash when they use APIs in unexpected ways. Re: When XUL is being ripped out Consequently, we have decided to deprecate add-ons that depend on XUL, XPCOM, and XBL. We don’t have a specific timeline for deprecation, but most likely it will take place within 12 to 18 months from now. " Re: The gap in capability "A major challenge we face is that many Firefox add-ons cannot possibly be built using either WebExtensions or the SDK as they currently exist. Over the coming year, we will seek feedback from the development community, and will continue to develop and extend the WebExtension API to support as much of the functionality needed by the most popular Firefox extensions as possible." ------------------------------- It's overly optimistic to assume add-on developers will have new versions ready in just a year if the API they're expected to rewrite everything in isn't even ready yet. I can understand why Mozilla is making this move, but it's being rushed. If WebExtension were ready today then this announcement would be more reasonable, but it's not even close! Hopefully Mozilla is just trying to scare their add-on developers into action, so they'll speak up and tell Mozilla exactly what they need from WebExtension. Starting over in a new API means a lot of existing add-ons will probably die anyways, but hopefully the important ones will make the move if Mozilla gives them enough time and support.