Design/Projects/Improve mobile reading experience

Providing a good reading experience is of high importance to Wikimedia projects. Typography, and specifically font choices, build the base for readability regardless of the device, software, or language of our readers.

Goals and summary
Our current font choice for sub-headlines and running text on mobile –   – builds on a generic font stack for historical reasons. This results in using Arial or Helvetica in latin languages on the majority of browsers. Both fonts mildly support the web's universality and have been the primary choice when supporting the widest variety of users like we do.

Driven by emerging mobile operating systems (OS) and strong growth in markets aside of latin script languages, in the last few years system manufacturers have been introducing new default fonts. These "system fonts" aim to provide better readability and better support for more languages.

These typefaces


 * deliver a better native experience for readers,
 * improve cross-platform and
 * improve cross-language readability.

We would like to use these system fonts in our selection fonts for the mobile interface presented by Minerva Neue.

Technical background
You can read more on the technical backgrounds in phab>phab:T175877|the Phabricator task.

Proposed system font stack (see discussion on task):

This CSS rule will apply the first font in the stack that is available. This is part of open web standards in most browser rendering engines. For example, Roboto is the Android operating system's current default font. None of the first three fonts are on Android systems by default. So, Roboto is selected for rendering the content.

To put another way the logic of this CSS rule: User system default > Wikimedia Design choice (Lato) > User operating system desktop only ( 'Helvetica Neue' > Helvetica > Arial) > generic sans-serif

Problem statement
Currently relying on web browser default font choice, which is, out of historical reasons often Arial and Helvetica as least common denominator with the widest language script support. But both fonts date back more than a dozen years.

Prior art
There have been a few other web institutions facing similar challenges and taken a similar path:
 * https://blog.cleartrip.com/2017/02/20/design-nuances-cleartrip-now-feels-more-at-home/
 * https://booking.design/implementing-system-fonts-on-booking-com-a-lesson-learned-bdc984df627f
 * https://medium.com/@vojtechjurasek/how-we-decided-to-use-system-fonts-87683b9b23ba