Analytics.js

Google Analytics.js Integration into <head></head>

Can be deleted if using an existing ga.js account, this one should be
used for new tracking accounts.

https://developers.google.com/analytics/devguides/collection/analyticsjs
/

“The analytics.js JavaScript snippet is a new way to measure how users
interact with your website. It is similar to the previous tracking
code, ga.js, but offers more flexibility for developers to customize
their implementations.”