Mozilla has decided to drop the support of Mac OS X 10.4 (Tiger) in future Firefox releases. This change will be introduced later this year when Firefox changes its rendering engine from Gecko 1.9.2 to Gecko 1.9.3.

Mozilla had already stop supporting Tiger in mozilla-central in September 2009. However, most of the code was left intact at the time in case they reversed their decision to drop Tiger support.

A lot of changes has happened in Mac OS X since Tiger was released in 2004. Mozilla want to embrace these new technologies but supporting Tiger at the same time is proving a hindrance.

According to the statistics published by Mozilla, about 24% of Firefox users on Mac runs Tiger. Mozilla says that dropping support for these users will not affect their market share significantly.

However, the main reason for dropping the Tiger support as said by Josh Aas, a Mozilla developer:

Adding 10.4 support back to mozilla-central would mean switching back to ATSUI from Core Text, switching back to gcc-4.0 from gcc-4.2, and doing a bit of porting work for code that has been added to the tree since we dropped support for 10.4. Other areas where 10.4 support consumes our time, makes our code more complex or error-prone, and/or limits our capabilities include complex text input (IME), out-of-process plugins, printing, native menus, and Core Animation. Furthermore, Apple's upcoming JavaPlugin2 will not support Mac OS X 10.4.

[source: mozilla.dev.planning]

[via: ars technica]