A message posted to Mozilla's mailing list by the company's Director of Firefox Engineeering, Johnathan Nightingale, has announced the company intends to reduce customizability with the Firefox browser for Android in order to increase performance. Firefox is transitioning from its XUL roots to the native Android code; the action marks a significant change for the browser, since Mozilla products have historically been built using XUL.
The new version of the browser will reduce the amount of customizability available, since previously created addons will not be compatible anymore. Developers will need to recreate their addons to take advantage of the rebuilt UI. The change from XUL, it is important to note, will not impact on the browser engine. Firefox for Android (or Fennec, as it is known) will continue to be built on the Gecko engine. The way in which the UI will be created is simply different.
Nightingale points out some of the new changes that will come from the UI design transition. Perhaps most appealingly for users of Firefox on Android, it will result in a faster boot time. Nightingale explains it as below:
A native UI can be presented much faster than a XUL based UI, since it can happen in parallel with Gecko startup. This means startup times in fractions of a second, versus several seconds for a XUL UI on some phones.
Firefox on Android is one of the heavier available browsers, so the news that the design will likely also reduce memory consumption can only serve to help its mobile market-share. Nightingale also admits that it is currently unknown when the new UI will be finished, but it will not impact on the versions in the Aurora and Nightly channels. It also will not impact upon the Tablet UI that the company are developing. Nightingale's full post can be read here.