Apple has apparently decided to kill support for OS X Snow Leopard, the 2009 operating system that has resisted retirement for more than a year.
On Monday, Apple did not update Safari 5.1 when it patched the later Safari 6 and 7 for newer editions of OS X, including 2011's Lion, 2012's Mountain Lion and this year's Mavericks.
Safari 5.1, which was last updated in September to version 5.1.10, is the most-current Apple browser for Snow Leopard.
Historically, Apple has patched Safari longer than the supporting operating system, so when the Cupertino, Calif. company calls its quits for the browser, it's already decided to retire the pertinent OS.
In July 2011, for example, Apple patched Safari 5.0 for the final time, updating the browser to version 5.0.6. That edition was the last that ran in OS X Leopard, which was released in October 2007.
Apple provided the final update to Leopard in June 2011.
The company did the same for OS X Tiger, officially known as OS X 10.4, which was retired from support in September 2009, more than four years after its introduction. Apple continued to update Safari 4, the newest version that ran on Tiger, for an additional 13 months, last fixing flaws in the browser in November 2010.
Snow Leopard was last updated with security fixes in September, the same day Apple last provided the final patches for Safari 5.1.
Traditionally, Apple has patched only the OS X editions designated as "n" and "n-1" -- where "n" is the newest available -- and discarded support for "n-2" either before the launch of "n" or immediately after. Under that plan, Snow Leopard was "n-2" when Mountain Lion shipped in mid-2012, and by rights should have been retired around then.
None of this would be noteworthy if Apple, like Microsoft, clearly spelled out its operating system support policies. But Apple doesn't, leaving users guessing about when their current Macs will drop into the unsupported dustbin.
"Let's face it, Apple doesn't go out of their way to ensure users are aware when products are going end of life," said Andrew Storms, director of DevOps at San Francisco-based CloudPassage, in an interview. "They live by the motto that users will just take all updates all the time as soon as they become available. Or users who are left in the dust will just go to the store and buy a new device."
The causes of Apple's longer-than-usual support for Snow Leopard are just as opaque -- Apple habitually declines to comment about anything related to security -- but analysts and experts have tapped several reasons.
One is Apple's accelerated release schedule, which now promises annual upgrades. The shorter span between editions means that unless Apple extended its usual support lifecycle, Snow Leopard would have fallen off the list less than three years after its launch.
Although Mavericks accounted for a third of all Mac operating systems last month, OS X Snow Leopard barely budged, powering 1 in 5 Apple personal computers. (Data: Net Applications.)
The second: Snow Leopard users have hung onto the OS. As of the end of November, more than 20% of all Macs globally were running that edition, slightly more, in fact, than ran its successor, Lion, which accounted for just 18%.
Snow Leopard users have given numerous reasons for hanging on, including ones identical to those expressed by some Windows XP customers: The OS still works fine for them, and their Macs, while old, show no sign of dying.
Also in play, however, is the fact that Snow Leopard was the last version of OS X able to run applications designed for the PowerPC processor, the Apple/IBM/Motorola-crafted CPU used by Apple before it switched to Intel in 2006. Snow Leopard, while incompatible with PowerPC silicon, is the most recent OS X that Apple lets run the Rosetta translation utility, and thus launch PowerPC software on Intel-based Macs.
Apple's support for even newer editions of OS X, including 2011's Lion and last year's Mountain Lion, has also come into question: In a very unusual move, the Cupertino, Calif. company declined to update either of those operating systems in October, when it released Mavericks with patches for more than 50 security vulnerabilities.
It's certainly possible that Apple has already pulled the plug on Lion and Mountain Lion, what with the two-month stretch without a sign of fixes for the bugs patched in Mavericks.
Because Apple made Mavericks a free upgrade from Snow Leopard, Lion and Mountain Lion, Apple could rationalize the dropping of support for the latter two.
"I'd call [Lion and Mountain Lion support] done. No update for you, pretty much means game over," Storms said.
Storms acknowledged that with Apple's silence, one can never be quite sure. In fact, as recently as June, Computerworld prematurely said that there was "little sign from Apple that it plans to stop patching Snow Leopard any time soon," only to be proved wrong six months later when Safari 5.1 missed the update bus.
For parts of Apple's customer base, the free-Mavericks strategy seems to be working: According to Web analytics company Net Applications, Mavericks' accounted for 32% of all versions of OS X used in November. Mavericks' gains, however, came at the expense of Mountain Lion -- which lost 18 percentage points last month -- and Lion, which dropped by 2.5 points. Yet Snow Leopard was unaffected by Mavericks. In November, OS X 10.6 fell less than either the 6- or 12-month average.
Bottom line: Only Apple knows who gets support, and who does not.
"If Siri could answer the question 'When is my OS going to stop being supported?' then we might know," said Storms. "Until then, the updates come and the updates go ... and the updates then stop."
Apple did not immediately reply to questions about its plans for Snow Leopard, Lion and Mountain Lion security support.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is email@example.com.
This story, "Apple signals end to OS X Snow Leopard support" was originally published by Computerworld.