Appendix: Context of Ads and Platforms in Each Country/Region
Description
We developed a systematic analytical framework to compare the functionalities, policies, terms of use and transparency mechanisms of ad networks from four big tech companies, digital platforms and search engines operating in the Brazilian market: Meta, Google, Twitter/X and TikTok. Our framework largely builds upon and, who argue that researchers are going through a time of low transparency and significant restrictions over data access imposed by online platforms and big tech companies. Based on the public documentation of each ad network, evidence found in journalistic reports and the existing academic literature, we present the responsibilities these ad networks delegate to advertisers, the permissions and restrictions of their targeting systems, their advertiser verification processes and the topics that can or cannot be promoted by advertisers. In particular, we pay attention to whether or not digital advertising repositories are available and the possibility of carrying out systematic investigations based on the provided data. That is, we consider that it is not enough to simply display and present the content of the advertisements to users, but to allow for systematically collecting available data and performing analysis in depth. In the cases in which ad repositories are available, we analyze their limitations regarding their searchability affordances, data access and data quality. Ultimately we analyze if researchers, journalists and other external auditors have found evidence of these protocols being carried out inappropriately, especially regarding the distribution of suspicious and irregular advertising.