Third Party Tracking in the Mobile Ecosystem

Reuben Binns, Ulrik Lyngs, Max Van Kleek, Jun Zhao, Timothy Libert∗, Nigel Shadbolt
Department of Computer Science, University of Oxford
*Reuters Institute for the Study of Journalism, University of Oxford


Third party tracking allows companies to identify users and track their behaviour across multiple digital services. This paper presents an empirical study of the prevalence of third-party trackers on 959,000 apps from the US and UK Google Play stores. We find that most apps contain third party tracking, and the distribution of track- ers is long-tailed with several highly dominant trackers accounting for a large portion of the coverage. The extent of tracking also dif- fers between categories of apps; in particular, news apps and apps targeted at children appear to be amongst the worst in terms of the number of third party trackers associated with them. Third party tracking is also revealed to be a highly trans-national phenomenon, with many trackers operating in jurisdictions outside the EU. Based on these findings, we draw out some significant legal compliance challenges facing the tracking industry.

Data harvesting and sharing by mobile apps is “out of control”:

  • Data tended to get concentrated by big companies and their subsidiaries.

  • More than 88% of free apps on Google Play shared information with firms owned by Alphabet.

  • Nearly 43% of apps shared data with Facebook, while significant percentages shared data with Twitter, Verizon, Microsoft and Amazon firms.

  • News apps - and apps aimed at children - shared information with the largest number of trackers.