Which font is the most widely used?

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Which font is the most widely used?

In print medium prior to the WEB it was probably a serif font, back in the day a item called a newspaper was printed every day of the year and a font called Times was the common newspaper “workhorse” font. So their was a lot of Times font widely used, stacks of bundles of papers printed using Times font.

Image from linotype article, Type Gallery - Times, https://www.linotype.com/259/times.html

Helvetica is a san serif font used very effectively by many graphic designers for half a century now. Helvetica was used for many way-finding systems and this is one way it became a well known type font. It was also one of the fonts provided early on as desktop computers came into use. It has been the basis of many recognizable logos, a part of many posters and publications too. The font Helvetica has come to have a wide and useful family of many weights, this makes it a very handy font to use and set type with and create many different looks. 
Starting in 1983 updated and reworked into Helvetica Neue and you saw it used as part of Apple macintosh computers and also in Apple iOS6 and iOS7.

In his answer to most widely used  Madhav Gopalan explained uses of Helvetica Neue, and listed some well know examples. One just can not deny Helvetica Neue is all over the web today too.

Another san serif font Arial is pretty common, it is often a default font in use on the web, and it is in the Windows, Mac and Linux OS. So it also is one of the top widely used fonts these days. Times New Roman also ranks as widely used by these qualifiers a web default and OS font. Yes it’s a modernized version of Times.

It would be difficult to tally most widely used, I would go with the trifecta, Arial, Times New Roman and Helvetica Neue.