The change will be visible with the latest major updates to both iOS 9 and OS X 10.11 operating systems, The Verge reported.
Helvetica Neue has been the default system font for iOS ever since the mobile OS received a dramatic redesign with iOS 7.
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This is not the first time that San Francisco, which was built by Apple with prime focus on legibility, has been moved beyond Apple watch.
San Francisco is meant to "maintain clarity and legibility" regardless of the size it's scaled to. The visual overhaul of OS X that started with Yosemite had generally been applauded, but Apple has been criticised for putting looks over usability with the move to Helvetica Neue .
