Appendix: Context of Ads and Platforms in Each Country/Region

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.本研究构建了一套系统性分析框架，用于对比运营于巴西市场的四家大型科技公司、数字平台及搜索引擎旗下广告网络的功能、政策、使用条款与透明度机制：Meta、Google、Twitter/X及TikTok。本框架主要基于相关研究立论——此类研究均指出，当前研究者正面临在线平台与大型科技公司施加的数据访问透明度不足、限制严苛的现实困境。本研究依托各广告网络的公开文档、新闻报道中的佐证材料及既有学术文献，梳理了这些广告网络赋予广告主的权责、定向投放系统的权限与限制规则、广告主验证流程，以及广告主可推广与不可推广的主题范畴。尤为重要的是，本研究关注数字广告库（digital advertising repositories）是否可用，以及基于所提供数据开展系统性调研的可行性。换言之，本研究认为，仅向用户展示广告内容远远不够，还需支持对可用数据进行系统性采集与深度分析。针对已开放广告库的平台，本研究进一步分析其在搜索功能可用性、数据访问及数据质量方面存在的局限。最终，本研究将调研研究者、记者及其他外部审计人员是否已发现相关协议执行失当的佐证，尤其是在可疑与违规广告投放场景中。