On other occasions we have already talked about this San Francisco font that debuted on the Apple Watch and that is destined to become the default font on all Apple systems.
San Francisco is specifically designed to be a fountain that have maximum clarity and be as readable as possible, of course it is still in the process of integration and is expected to reach all three Apple systems in the fall.
Particularly the current Helvetica Neue font seems to me to be accurate enough for Apple to keep it as the default on OS X because even if it fails in readability for small sizes, the new HiDPI displays are detailed enough that this is not a problem. Still change is always good and I don't dislike San Francisco at all.
In addition to the font chosen, San Francisco supports a kind of dynamic adjustment that adapts both in height depending on the size chosen and in line spacing. Along with the San Francisco typeface, Apple's system fonts web page offers developers access to the TextKit API for font handling, the Apple Font Tool Suite and all specifications for the TrueType and Apple Advanced Typography (AAT) font format from the Typeface Registry.
The company has previously released a version of the San Francisco font for developers on the Apple Watch along with Photoshop templates to create application graphics.
Developers can download Apple's new San Francisco font packs via the developer portal.