Besides fixing twenty-nine security vulnerabilities, Firefox 55 adds support for the virtual reality technology WebVR, some new performance-related settings, and improvements to address bar functionality. The sidebar can now be on the right side of the browser, instead of only on the left. The Print Preview function now includes options for simplifying what’s printed. Starting Firefox with multiple tabs is now much faster. The Flash plugin is now ‘click to activate’ and only works with regular web and secure web URLs.

The default installation process has been modified, to simplify and ‘streamline’ installation for most users. Traditional, full installers are still available. The somewhat-less-likely-to-crash 64-bit version of Firefox is now installed by default on 64-bit systems with at least 2 GB of RAM.

Mozilla steadfastly refuses to mention version numbers in Firefox release announcements (including the one for Firefox 55), or to announce all new versions. Their rationale seems to be that the information exists somewhere, therefore they have done their job. Combined with the unpredictability of Firefox’s internal update mechanism, this is an ongoing frustration for some users (possibly only me).

On that subject, I’m still waiting for my installation of Firefox to notice that a new version is available. Firefox 55 includes changes to the browser’s built-in update process, but it’s not clear whether those changes will actually improve things. From the release notes: “Modernized application update UI to be less intrusive and more aligned with the rest of the browser. Only users who have not restarted their browser 8 days after downloading an update or users who opted out of automatic updates will see this change.”

Update 2017Aug13: According to denizens of Mozilla’s official #firefox IRC channel, the Firefox update servers have been disabled because of some problems with Firefox 55. Of course, Firefox will continue to tell you that “Firefox is up to date”, which can mean several different things. There’s no word on when the update servers will be back online, or what the problems are, but a search of the bug list for Firefox shows a likely candidate: Tabs are all restored as blank frequently after restart of [sic] applying Firefox 55 update. Apparently after upgrading to Firefox 55, some users are having problem restoring tabs, and in some cases, profile information is lost. Recommendation: don’t jump the gun and install Firefox 55 manually. Wait for the next version, which will likely be 55.0.1 or 55.0.2.

Update 2017Aug15: A new post on the Mozilla blog (64-bit Firefox is the new default on 64-bit Windows) confirms that 64-bit Firefox is now the default for 64-bit Windows systems, and that the 64-bit version is much more stable than its 32-bit equivalent. It goes on to say that to get the 64-bit version, you can either download and install it manually, or “You can wait. We intend to migrate the remaining 64-bit Windows users to a 64-bit version of Firefox with a future release.” No word on just how long we’ll have to wait.

Update 2017Aug17: Today, my install of Firefox started showing 55.0.2 as the latest version on its Help > About dialog. I went ahead and let it update itself, and now I’m running the 32 bit version of 55.0.2. According to the release notes, Firefox 55.0.1 fixes the bug in the tab restoration process that was introduced in 55.0. Firefox 55.0.2 fixes a problem with profiles that was introduced in 55.0.