The ping attribute has been a part of the HTML standards since 2010. But, few people know about it. However, it is a very useful way to simplify individual event tracking – the capture of behavioral data. From our perspective the trend is going away from standard web analytics packages. Instead, we are recommending that our customers capture and analyze their data themselves. It is simpler and more flexible than with a tool, which abstracts relatively limited meaning from your data.
When you use this attribute and the user clicks on a link, then the browser sends a request in parallel to the URL which is indicated in the ping attribute. That could even be multiple URLs: "The ping attribute, if present, gives the URLs of the resources that are interested in being notified if the user follows the hyperlink. The value must be set to space-separated tokens, each of which must be a valid non-empty URL. The value is bused by the user agent for hyperlink auditing."
<a href="https://widgetsinc.com/super-gizmo" ping="https://google.com/click?=https://widgetsinc.com/super-gizmo">
Google uses this to eliminate the need for a redirect to a mobile search result. Via the ping attribute a click will be sent for tracking purposes to Google. However, the mobile browser can be sent directly to the corresponding URL. This saves roughly 200 to 400 ms per click.