San Francisco (sans-serif typeface) and iOS 10 is a new variant named "SF Compact Rounded". It is used in the new contact placeholder icons introduced in the OSes. The "SF Serif" variant was showcased during the keynote at WWDC 2018 on June 4, 2018 when the all-new Apple Books app was introduced. This variant is exclusive to Apple Books in iOS 12 and macOS Mojave, is not mentioned in Apple's Typography design guidelines, and is not publicly downloadable like other variants of the San Francisco typeface. Since its introduction, San Francisco has gradually replaced most of Apple's other typefaces on their software and hardware
Helvetica stroke widths within a glyph. Nimbus Sans L, a version of URW's Nimbus Sans spaced to match the standard Linotype/PostScript version of Helvetica, was released under the GNU General Public License in 1996, and donated to the Ghostscript project to create a free PostScript alternative. It (or a derivative) is used by much open-source software such as R as a system font. A derivative of this family known as "TeX Gyre Heros" has been prepared for use in the TeX scientific document preparation software. FreeSans, a free font descending from URW++ Nimbus Sans L, which in turn descends from Helvetica.