With Firefox preparing to leave behind OS X 10.6 Snow Leopard, 10.7 Lion, and 10.8 Mountain Lion after Firefox 45 ESR* is replaced by the next Extended Support Release, I suggested it might be time for the Mac community to develop a branch of Mozilla that continues to support Snow Leopard. But maybe not.

There are several factors to take into consideration that mitigate against Mozilla continuing development for Firefox for these versions of OS X:

• Firefox is already having problems on OS X 10.6. “…we’re seeing intermittent and permanently failures on MacOS 10.6 that we are not seeing elsewhere.”
• With relatively few Snow Leopard, Lion, and Mountain Lion users (1.2% of all Mac users), Mozilla cannot justify investing resources in increasingly outdated versions of the Mac OS.
• Current versions of Xcode development software (and possibly other development tools as well) no longer support OS X versions prior to 10.9 Mavericks.
• All OS X 10.8 users can upgrade to OS X 10.9 Mavericks, 10.10 Yosemite, and 10.11 El Capitan for free.
• Apple no longer provides any support for these versions of OS X.

Of the three versions of OS X being deprecated, 10.6 Snow Leopard represents about 55% of those Firefox users. About 30% are using 10.7 Lion. And the 15% on Mountain Lion can migrate to a currently supported version of OS X for free.

But Wait a Minute

Among Low End Mac users on OS X 10.6 and higher, our February site logs show 10.6 at 11.7%, 10.7 at 6.4%, and 10.8 at 3.1%, so for us, that’s over 21% vs. 1.2% among Firefox users. (Less than 3% of Intel Mac users visiting lowendmac.com are using OS X 10.4 or 10.5.) We obviously represent a very different demographic than users of currently supported versions of Firefox.

In our community, the percentage of Snow Leopard users has risen slightly over the past two months. Lion is pretty steady, and Mountain Lion is shrinking away as more users upgrade to a more recent version of OS X. Snow Leopard users are a solid audience, and at this point most Lion users are on Macs that don’t support anything newer.

Can’t Snow Leopard Already Run TenFourFox?

Perhaps the best reason against compiling a version of Firefox for OS X 10.6 users is that Snow Leopard includes Apple’s Rosetta software, which translates PowerPC code to Intel code on the fly, allowing us to run PowerPC-only software on Intel Macs running OS X 10.4 Tiger, 10.5 Leopard, and 10.6 Snow Leopard.

There’s one problem there: Firefox is dropping OS X 10.6, 10.7, and 10.8 with Extended Support Release 45, which will give us about one more year of support. TenFourFox will also stop development after Firefox 45 because Firefox 46 and beyond will include Electrolysis (e10s) to provide faster, more secure access to content.

TenFourFox will use Firefox 45 as its core going forward, adding what features it can from future releases but ignoring Electrolysis because it cannot be supported by OS X 10.4 Tiger. Going forward, Snow Leopard users can stick with the official Firefox 45 ESR or run TenFourFox via Rosetta – using the same core available in a native Intel Mac build, although TenFourFox may be more stable on OS X 10.6.

Should We Pursue TenSixFox?

Snow Leopard is a legacy version of OS X. It can run on the oldest Intel Macs. It’s the last version with Rosetta. It’s less demanding than OS X 10.7 Lion. It’s going to remain in use for years to come, just as some Windows users are still on XP.

If Electrolysis won’t function on Intel Macs using OS X 10.6, I really see no point to developing TenSixFox as a separate project. If that’s the case, it probably makes more sense to develop a fork of TenFourFox for Intel Core Duo and Core 2 Duo Macs.

On the other hand, if Electrolysis can work with Snow Leopard and Lion, it would be great to see Firefox 46 and beyond compiled for these older operating systems that Apple, Google Chrome, and Mozilla no longer choose to support.

If anyone knows more about the possibilities of Electrolysis and Firefox 46 and beyond under OS X 10.6 and 10.7, please leave us a comment. Thanks!

 * Firefox is currently at version 45.0.1.

Update

There is a set of Intel-only builds based on TenFourFox:

• TenFourFox is only for OS X 10.4 Tiger on Intel Macs
• TenFiveFox is only for OS X 10.5 Leopard on Intel Macs
• TenSixFox is only for OS X 10.6 Snow Leopard, 10.7 Lion, and 10.8 Mountain Lion

Further Reading: TenFourFox Development Blog

• Status Update, August 2014
• Electrolysis means splitsville, November 2014
• Après moi, le Tier-3 holocaust, March 2016

Keywords: #tensixfox #tenfourfox #firefox45esr #electrolysis #e10s

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