Figure 2 from: Jones T, Baxter D, Hagedorn G, Legler B, Gilbert E, Thiele K, Vargas-Rodriguez Y, Urbatsch L (2014) Trends in access of plant biodiversity data revealed by Google Analytics. Biodiversity Data Journal 2: e1558. https://doi.org/10.3897/BDJ.2.e1558

Figure 2 - Four variants of GA are represented in this study. Urchin is the first iteration of GA, derived from software developed by Urchin Software acquired by Google in 2005. It is unique in that it employed multiple means of information gathering, using both server logs and multiple cookies. The second iteration, synchronous or traditional, released in late 2007, also used multiple cookies, plus required that the JS load in a linear fashion. Penalizing content over tracking. Asynchronous came out two years later, and allowed for faster loads of content as the webpage loads first, and GA JS loads post-content delivery. The latest variant, universal, addresses issues with mobile and the internet-of-things (emerging wearable devices and existing household appliances that can communicate via the web), as it can assimilate into reports any device that can contact a server.