A Year Under the DSA: Ad Transparency's Uneven Landscape
Authors: Abir Benzaamia (LIX, CNRS, Inria, École Polytechnique, IP Paris), Asmaa El Fraihi (LIX, CNRS, Inria, École Polytechnique, IP Paris), Ines Abdelaziz (LIX, CNRS, Inria, École Polytechnique, IP Paris), Oana Goga (LIX, CNRS, Inria, École Polytechnique, IP Paris)
Volume: 2026
Issue: 2
Pages: 517–532
DOI: https://doi.org/10.56553/popets-2026-0059
Abstract: The Digital Services Act (DSA) has put platform accountability on center stage, requiring online platforms to provide greater transparency into how advertisements are targeted and delivered to users. Central to these obligations are two mechanisms: user-facing ad explanations, which inform individuals why they were shown a given ad, and public ad repositories, which are intended to enable independent auditing of advertising practices. This study provides the first multi-platform evaluation of these two mechanisms across Facebook, Instagram, YouTube and X. Using 48,511 user-facing “Why am I seeing this ad?” (WAIST) notices, and a systematic analysis of each platform’s public ad repository, we assess how well current implementations disclose the parameters and decision processes involved in targeting. To do so, we develop and apply an operational framework based on Articles 26 and 39 of the DSA—capturing the granularity, attribution of targeting and delivery choices, data source disclosures, and accuracy—and apply it across both user-facing notices and public ad repositories. Our findings show that transparency remains fragmented and inconsistent across platforms. User-facing explanations vary widely in precision and often omit key targeting information, while repositories provide incomplete, misattributed, and at times difficult-to-interpret targeting data. Moreover, discrepancies between explanations and repository entries undermine the reliability of both mechanisms. Overall, current transparency infrastructures fall short of the DSA’s expectations and highlight the need for clearer and more enforceable standards for advertising transparency moving forward.
Keywords: Digital Services Act (DSA), Online Advertising, Ad transparency, Ad explanations, Ad repositories
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