Greasy Fork is available in English.
Replaces Arial with Helvetica on all webpages
This style removes all traces one of the worst fonts of all time, Arial, and replaces it with the similar but better looking font Helvetica. Arial was designed to be "metrically compatible" with Helvetica, which basically means the two fonts' characters take up the same amount of space. This and their similar appearances mean that the fonts can be substituted for each other without problems.
For more anti-Arial propaganda, see https://www.marksimonson.com/notebook/view/the-scourge-of-arial
This script really only works on Mac, because 99% Windows and Linux PCs don't have Helvetica installed, and even if they do, their font renderers make it so Arial actually looks better than Helvetica on those systems.
Tested on the following configuration:
Licensed under CC0 public domain dedication: https://creativecommons.org/publicdomain/zero/1.0/
