Firefox 26 has been out for some days now, a rather unspectacular update for many users as it does not really ship with that many new or improved features.
One of the changes in Firefox 26 that I did not mention in the review is the removal of the old download manager API.
Mozilla did introduce a new download manager API in Firefox 20 to resolve performance issues of the old, but did not remove the old API immediately.While the new download panel was the default way that downloads were handled in Firefox 20 and newer, there was still a way for users to use the old download manager interface instead.
The old download manager opened in a window instead of in a panel inside the browser window. Firefox users had to switch the preference browser.download.useToolkitUI in about:config to true to use the old API instead of the new one.
The option to do so was removed in Firefox 26, leaving some users puzzled in the process.
Removal of the old API
Several download manager extensions did make use of the old download manager API as well, and when Firefox 26 came along, users noted that extensions were broken and did not work properly or at all anymore.
So, users who made use of the preference switch in Firefox to use the old interface noticed that this was not possible anymore, and users who ran download manager extensions may have also noticed that theirs stopped working.
A popular extension that stopped working is Download Statusbar. The page of the extension on Mozilla Add-ons displays that it is used by more than 1.6 million Firefox users.
It was originally designed for Firefox 4, as Mozilla did remove the status bar in the browser to replace it with the add-ons bar instead.
It is not the only extension though. Basically, if an extension has not been updated for some time now then it is very likely that it won't support the new API. In the case of Download Statusbar, it has been last updated in 2011.
Anyway, since it relies on the old API, it is currently not working anymore and the only hope for Firefox users to resolve the issue is to either wait for the developer to release an update for it, or to switch to another extension that makes available the same functionality.
Download Status Bar is that extension in the case of Download Statusbar. It is a work in progress as noted by the developer on the AMO website.