In September 2017, I wrote that the scroll depth would be a better indicator of whether a piece of content has been read than the pure session duration, which is nonsense anyway. A month later, Google then released a new feature in Google Tag Manager, a trigger for the visibility of elements (the note was missing in the German version of the release notes). This compensates for some disadvantages of the scroll depth approach, especially the restriction that not every page is the same length and “75% read” does not always mean that the content was read to the end (75% was chosen because many pages have an immense footer and therefore users do not scroll down 100%). A page on mine has so many comments that they make up more than half of the content.
What does element visibility mean?
In simple terms, this feature means that a trigger is triggered when an element of the page becomes visible on the user’s screen. The element only needs to be uniquely named, so that only this one element with this name can trigger the trigger. On my site, for example, I would like to know how many users have scrolled down so far that they have finished reading the respective text with a high degree of probability. This is probably the case when users see the reference to the similar articles that are created in my blog by the YARPP plugin. In most browsers, it is possible to select an element with the mouse and then examine the element with a right-click/CTRL click on it, so that we can then see exactly what that element is called.
