Mozilla is making progress on adding a silent update mechanism to Firefox, with plans to integrate the new service in Firefox 10 early next year.
But one of the developers working on the feature cautioned that silent update might slip.
"At this point, we're not quite sure which version of Firefox this will land in. We're working to land it as soon as is safely possible," Ehsan Akhgari, a Firefox engineer in charge of one of the silent update components, said in a blog post last weekend.
Akhgari's part of the project is to minimise the amount of time it takes Firefox to launch after downloading an update.
To do so, he's come up with a way to stage the downloaded update - essentially an updated copy of Firefox - in a separate Windows directory, then swap the older edition with the newer one the next time the user starts up Firefox.
Silent update development
Other pieces to the silent update puzzle include installing a Windows service so an update doesn't trigger a UAC (user account control) prompt message and setting all add-ons as compatible by default, again so that Firefox doesn't display a warning message.
According to information on the Mozilla website, the current goal for most of the multi-part project remains Firefox 10, slated to ship on January 31, 2012. Some pieces, however, have already appeared in release versions - Firefox 8 implemented a pair of peripheral components - while others may not land in the browser until after Firefox 10.
For example, the sidestepping of Windows Vista's and Windows 7's UAC prompts is currently "at risk" for making it into Firefox 10, although notes from a status meeting Mozilla held this week indicate that the feature should wrap up this week and move to testing.
If all parts of silent update don't make it into Firefox 10, the next available release dates would be March 13 for Firefox 11, and April 24 for Firefox 12.
Mozilla has been working on silent updating for more than a year. At one point, it thought it could add the feature to Firefox 4, which shipped in March 2011, but abandoned work when that version was delayed several times for other reasons.
'Rapid release' schedule
Implementing silent updating would make Firefox only the second browser to offer the feature. Google's Chrome has used automatic, in-the-background updates since its September 2008 debut.
Silent updating would let Mozilla deploy emergency security fixes - it called them "chem spills" - without bothering users, as well as theoretically dragging more of them along to the next version.
Chrome's automatic updating, for example, has patched the browser three times in the last 30 days: October 25, November 10 and November 16.
Mozilla has done a credible job getting most users to upgrade even without silent updates, but its every-six-week release schedule is leaving more users behind.
According to web metrics firm Net Applications, Firefox 7 - which launched on September 28 - made up 46% of all copies of the browser used last month. However, the "tail" of those running older editions, Firefox 4 through Firefox 6, grew during October to 23%, a 10% jump from the month before.
One in four Firefox users is still running version 3.6, the January 2010 edition. Mozilla was to kick off a major campaign last week designed to push those users to upgrade to Firefox 8, but for the second time postponed the offer, this time to await a pair of patches to the latter.