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An ad-transparency archive is a repository, published by an advertising platform, of the ads it carried: the creative, who paid, when it ran, and sometimes how it was targeted and how many people saw it. Meta's Ad Library, Google's Ads Transparency Center, TikTok's Commercial Content Library and the ten other repositories the Digital Services Act obliges are all of this kind.
For a measurement researcher, an archive is an unusually good instrument and an unusually treacherous population. It is good because it is bulk, retrospective, queryable and free: no crawler, no sock puppets, no rate limit worth the name, and a window that reaches years further back than you could ever crawl. It is treacherous because the platform decides what goes in it, using a classifier of its own, and both directions of that classifier's error land in your denominator. A prevalence computed on an archive is a prevalence among ads the platform put in the archive, which is not the same as ads that ran, and is very much not the same as ads that were submitted.
This page is about that gap: which archives exist and what each one covers, what an archive structurally cannot contain, how the field has measured the archives' own error rates, and what you have to hold alongside an archive to say anything about the ads it is missing. It is a child of Platforms, which covers the other ways into a platform; the archive is the one route that page identified as a distinct instrument deserving its own treatment.
The corpus figure this page's parent published was wrong, and the correction is the point. Platforms reports “69 papers name an Ad Library or ad archive”, from a full-text probe for /Ad Library|Ads? Archive API/i. That probe is defeated by a homonym. In mobile-security writing an “ad library” is an advertising SDK linked into an Android app; in platform-transparency writing “the Ad Library” is Meta's public ad archive. Of the 69, 44 contain only the lowercase SDK sense, and the probe additionally matches the substring inside “re[ad librar]y”.
Hand-auditing every candidate paper against its own full text gives the real number: of the 5,855 papers in the publication corpus with extractable full text (seven venues, 2010–2026), 11 use an ad-transparency archive as a data source or measure the archive itself. Eight more mention one only in their bibliography. The old probe's precision for this question was 14.5%.
Eleven papers is a small literature, and this page says so rather than inflating it. But it is a coherent eleven — four of them measure the archive's own accuracy, and they agree — and it is growing: 2 papers in 2020, 4 in 2023–2024, 3 in 2025–2026.
If you are planning an EU political-ad study in 2026, read The Regulatory Floor, and the October 2025 Cliff first. Both Meta and Google stopped carrying political advertising in the EU in October 2025 in response to Regulation (EU) 2024/900. The historical ads stay in the archives; new ones do not arrive. Every EU political-ad paper in this corpus studies a window that has closed.
Five papers. The first four are chosen because each attacks the archive's accuracy from a different side; the fifth is what you do when you decide the archive cannot answer your question.
This is the first thing to get straight, because the four have different populations, different failure modes, and live on different pages of this wiki. Papers use them interchangeably in prose and not at all interchangeably in method.
| Instrument | Unit of observation | Population you get | Who it comes from |
|---|---|---|---|
| Ad archive / repository — Meta Ad Library, Google Ads Transparency Center, TikTok Commercial Content Library | one ad (creative + advertiser + run dates + aggregate reach) | ads the platform classified into the archive and did not remove | the platform, in bulk, retrospectively |
| Per-impression explanation — “Why am I seeing this ad?”, About this ad | one impression shown to one identified user | ads you were shown, with the platform's account of why | the platform, one impression at a time, only to the recipient |
| Ad-preference or ad-settings panel — Google My Ad Center, Meta ad preferences | one inferred attribute about one user | the profile the platform admits to holding | the platform, per account |
| Donation or crowdsourced ad corpus — Who Targets Me, Ad Observer, Australian Ad Observatory | one impression, pooled across consenting users | ads real users actually saw, with a panel-shaped bias | a browser extension, not the platform |
The confusion is not academic. [6Bryson, Kevin; Borem, Arthur; Moh, Phoebe; Akgul, Omer; Edelson, Laura; Lauinger, Tobias; Mazurek, Michelle L.; McCoy, Damon; Ur, Blase (2025): "Characterizing the Usability and Usefulness of U.S. Ad Transparency Systems", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] (IEEE S&P 2025) is a usability study of 22 US ad-transparency systems — the second and third rows, not the first — and finds that “more than two-thirds of all questions and more than half of desired actions went unanswered or unaddressed”. [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] measures the second row (48,511 explanations) and uses it to audit the first. [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)] (PoPETs 2026) wanted the first row as ground truth for an experiment on the second and concluded it could not be used. If you write “ad transparency” in a methods section without saying which of the four you queried, a reviewer cannot tell what your denominator is.
For the third row see consent and Platforms; for the fourth, Biases on what a donation panel is a sample of.
Thirteen services designated as very large online platforms in April 2023 publish an ad repository because DSA Article 39 requires one. They are not comparable instruments, and the differences are exactly the ones that decide whether your study is possible.
The Papers column counts papers in this corpus that used or measured the archive, from the hand-audit in Use in Publications. Statuses and scopes were checked against each provider's own documentation on 2026-09-08; every URL and quote is on ad_archives.
| Archive | Scope | Bulk access | Retention | Papers |
|---|---|---|---|---|
| Meta Ad Library 1) | social-issue, election and political ads worldwide, plus ads of any type delivered to the UK or EU | Ad Library API (Graph API), plus a web portal and an aggregate Ad Library Report | political ads 7 years; UK/EU ads of any type 1 year | 8 |
| Google Ads Transparency Center 2) | all ads from advertisers serving on Search, Display, Gmail and YouTube; a separate political section restricted to verified election advertisers | web interface; the political subset is “published as a public data set on Google Cloud BigQuery” | election ads 7 years after last impression | 3 |
| TikTok Commercial Content Library 3) | paid ads and other commercial content, EU countries only | Commercial Content API, by application | not stated on the access page | 0 |
| X Ads Repository 4) | commercial communications served in the EU | full-dataset CSV download, no application | not stated | 0 |
| Apple App Store Ad Repository 5) | App Store ads | web; free without an account per [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)]'s cited stress test | not stated | 1 |
| LinkedIn Ad Library 6) | ads served on LinkedIn | web | back to its DSA obligation date | 0 |
| Microsoft / Bing Ad Library 7) | Bing ads | web | not stated | 0 |
| Snapchat Ads Gallery 8) | Snapchat ads | web; no API as of the Mozilla stress test | not stated | 0 |
| Pinterest, Booking.com, AliExpress, Amazon, Zalando 9) | that platform's own ads | mixed; AliExpress had no API as of the stress test | mostly back to the DSA obligation date | 0 |
| The EU “European repository for online political advertisements” | in principle all political ads published in the EU, from publishers large and small | a common data structure and API were specified by Commission Implementing Regulation (EU) 2026/818 of 9 April 2026 10) | transparency notices 7 years after last publication (Reg. 2024/900 Art. 12) | 0 |
Three readings of that table matter more than the rows.
The one independent cross-platform comparison is not from these venues: Mozilla commissioned Check First to stress-test all thirteen against DSA-derived criteria, published 16 April 2024, and concluded that “even the best approaches don't meet our baseline” and that “our accuracy testing found many cases where ads in the user interface were not located in the ad repository”.11) It is now two years old, which is why the statuses above were re-checked rather than taken from it — but it is the only source that has tried all thirteen, and it should be your starting inventory rather than a vendor listicle.
This is the part to put in your paper as a limitation, and the part reviewers of archive studies now ask about. None of these are bugs; they follow from what an archive is.
The denominator sentence an archive study needs. Not “we analysed N ads from the Ad Library” but: N ads that platform P placed in archive A between d1 and d2, for region R, under P's own definition of category C, excluding ads P removed. Every clause in that sentence is a place your prevalence differs from the world's. Write it out once in Section 3 and every later percentage is interpretable.
An archive built around a category — “political”, “social issue”, “election” — is the output of a classifier the platform runs and does not publish. That classifier has a false-positive rate and a false-negative rate, and an archive study inherits both. Papers that report only one of them are reporting half the error.
Four papers in this corpus have measured it. They used different platforms, years, regions and ground truths, and they agree that both rates are large.
| Study | What was measured | Miss rate (false negatives) | Over-inclusion (false positives) | Denominator the paper used |
|---|---|---|---|---|
| [1Edelson, Laura; Lauinger, Tobias; McCoy, Damon (2020): "A Security Analysis of the Facebook Ad Library", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] IEEE S&P 2020 | disclosure completeness inside the US political archive | 68.3% of pages ran at least one undisclosed political ad that was only later detected and added | — (measured attribution error instead: 15.8% of spend, $98.2 M, unattributable or misattributable) | 126,013 pages with ads in the Ad Library; 3,685,558 ads, May 2018 – June 2019 |
| [8Silva, Márcio; Oliveira, Lucas Santos de; Andreou, Athanasios; Melo, Pedro Olmo Stancioli Vaz de; Goga, Oana; Benevenuto, Fabrício (2020): "Facebook Ads Monitor: An Independent Auditing System for Political Ads on Facebook", in: Proceedings of the ACM Web Conference. (DOI)] TheWebConf 2020 | archive recall against an independent collector | only 34 of 835 ads their classifier called political had a matching ad in the archive | — | 38,110 ads collected from volunteers in Brazil, 2018 |
| [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)] USENIX Sec 2022 | Facebook's own political-ad enforcement | 4.5% worldwide; 0.85% in the US against up to 45% elsewhere | 55% of ads Facebook flagged as political in the US were not political | 33.8 M ads observed; 4.2 M political and 29.6 M non-political from all 215,030 pages that ran political ads |
| [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] IMC 2024 | Meta's EU moderation under the DSA | 92.3% of undeclared political ads were not moderated as political (recall 7.7%) | 60.4% of the ads Meta did moderate did not match Meta's own criteria | all EU ads via the Ad Library API, Aug 2023 – Feb 2024; 29.5 M ads used for inference |
| [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] PoPETs 2026 | repository completeness against donated impressions | 48% of Facebook ads and 9% of Instagram ads seen by real users were missing from the repository | — | 351 Facebook and 438 Instagram ads matched from 48,511 donated ad explanations |
Three consequences for a study design, in the order they will bite you.
Since the archive cannot tell you what it is missing, an archive study needs a second, independent view of the same ads. The field has used four, and they trade off in the obvious way: the closer you get to what a real user saw, the smaller and more biased your sample.
| Second view | What it buys | What it costs | Used by |
|---|---|---|---|
| Donation panel — a browser extension on consenting users' real sessions | ads as actually delivered, with the per-impression explanation attached | population is whoever installed the extension: a convenience sample with an activist skew | [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] (Who Targets Me), [9Ali, Muhammad; Goetzen, Angelica; Mislove, Alan; Redmiles, Elissa M.; Sapiezynski, Piotr (2023): "Problematic Advertising and its Disparate Exposure on Facebook", in: Proceedings of the USENIX Security Symposium. (Link)] and [10Chen, Baiyu; Tag, Benjamin; Xue, Hao; Angus, Daniel; Salim, Flora (2026): "When Ads Become Profiles: Uncovering the Invisible Risk of Web Advertising at Scale with LLMs", in: Proceedings of the ACM Web Conference. (DOI)] (Ad Observer / Australian Ad Observatory) |
| Your own ad campaign — buy ads with known parameters, then look for them | exact ground truth about targeting, spend and category, because you set them | you are an advertiser now: money, platform terms, ethics review, and it does not scale | [5Gkiouzepi, Eleni; Andreou, Athanasios; Goga, Oana; Loiseau, Patrick (2023): "Collaborative Ad Transparency: Promises and Limitations", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)], [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)], [11Venkatadri, Giridhari; Sapiezynski, Piotr; Redmiles, Elissa M.; Mislove, Alan; Goga, Oana; Mazurek, Michelle L.; Gummadi, Krishna P. (2019): "Auditing Offline Data Brokers via Facebook's Advertising Platform", in: Proceedings of the ACM Web Conference. (DOI)] |
| Independent crawl or collector — find ads yourself and match them back | catches ads the archive never received; works where no panel exists | matching is the hard part, and a failed match is ambiguous between “missing” and “not matched” | [8Silva, Márcio; Oliveira, Lucas Santos de; Andreou, Athanasios; Melo, Pedro Olmo Stancioli Vaz de; Goga, Oana; Benevenuto, Fabrício (2020): "Facebook Ads Monitor: An Independent Auditing System for Political Ads on Facebook", in: Proceedings of the ACM Web Conference. (DOI)], [12Zeng, Eric; Wei, Miranda; Gregersen, Theo; Kohno, Tadayoshi; Roesner, Franziska (2021): "Polls, Clickbait, and Commemorative \$2 Bills: Problematic Political Advertising on News and Media Websites Around the 2020 U.S. Elections", in: Proceedings of the ACM Internet Measurement Conference. (DOI)], [13Bitaab, Marzieh; Karimi, Alireza; Lyu, Zhuoer; Oest, Adam; Kuchhal, Dhruv; Saad, Muhammad; Ahn, Gail-Joon; Wang, Ruoyu; Bao, Tiffany; Shoshitaishvili, Yan; Doupé, Adam (2025): "ScamMagnifier: Piercing the Veil of Fraudulent Shopping Website Campaigns", in: Proceedings of the Network and Distributed System Security Symposium. (Link)] |
| The platform's own moderation labels — compare declared against detected | free, and it is the platform grading itself, which is the auditable claim | only exists where the platform publishes a moderation signal, which in practice means Meta political ads | [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)], [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] |
Two practical notes. Matching is where these studies actually fail, not collection: [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] links each donated ad to a repository record “when a unique match can be determined using shared identifiers”, and its headline 48%-missing figure is really “48% we could not uniquely match”, which is an upper bound on missingness. Say which it is. And the donation route is the one that is growing — 25 papers in this corpus mention data donation, 11 of them in 2025 — but only 4 mention Who Targets Me and 5 Ad Observer or an Ad Observatory, so the panels themselves are still nearly unused in these venues.
Both Who Targets Me and Ad Observer were still operating when checked on 2026-09-08; the Australian Ad Observatory's first phase closed in March 2024 and a second phase runs to 2027.13)
Ad archives are one of the few measurement instruments on this wiki that exist because a law requires them, which means their scope is set by legal text you can read rather than by product decisions you cannot.
For services the European Commission has designated as very large online platforms or search engines, Article 39 of the Digital Services Act requires an ad repository “through a searchable and reliable tool that allows multicriteria queries and through application programming interfaces”, covering “the entire period during which they present an advertisement and until one year after the advertisement was presented for the last time”. The mandated fields are the ad content, the person it is presented on behalf of, the payer if different, the run period, whether it was targeted “including where applicable the main parameters used to exclude” groups, branded content identified under Art. 26(2), and “the total number of recipients of the service reached and, where applicable, aggregate numbers broken down by Member State”.
Three things follow that a fresh reader gets wrong.
The EU's political-advertising regulation — Regulation (EU) 2024/900, the “TTPA” — applies from 10 October 2025 and mandates a European repository for online political advertisements run by the Commission, with transparency notices retained “for a period of seven years after the last publication”. Commission Implementing Regulation (EU) 2026/818 of 9 April 2026 sets out its common data structure and API.
Both of the platforms whose archives this entire literature is built on responded by leaving the market.
For a measurement plan in 2026 the consequences are concrete, and they cut in opposite directions.
All figures below come from the publication corpus of seven venues (CCS, IMC, NDSS, PETS, USENIX Security, TheWebConf, IEEE S&P), 2010–2026, 5,859 extracted papers of which 5,855 have extractable full text. The script is scripts/adarchives_report.mjs and its unedited output, every query and the full hand-audit are on ad_archives.
A paper counts if an ad-transparency archive is a data source for it, or if the archive itself is what it measures. A bibliography entry does not count. A mention of an Android advertising SDK does not count, and that is the whole problem: “ad library” is a homonym, and the SDK sense is far more common in these seven venues than the archive sense.
| What /Ad Library|Ads? Archive API/i actually matched, over 5,855 full texts | Papers |
|---|---|
| an Android advertising SDK (lowercase “ad library”, “ad libraries”) | 44 |
| the proper noun “Ad Library” somewhere in the text | 25 |
| total — the figure Platforms published | 69 |
Auditing all 29 papers matched by a wider, case-sensitive candidate probe against their own full text:
| Verdict | Papers | What these are |
|---|---|---|
| archive as instrument or as object | 11 | the audited set this page reports |
| bibliography or related-work mention only | 8 | six of them cite [1Edelson, Laura; Lauinger, Tobias; McCoy, Damon (2020): "A Security Analysis of the Facebook Ad Library", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] and nothing else |
| Android advertising SDK | 8 | e.g. a table column headed “Ad Library” listing AdMob and Unity |
| an ad archive in another sense | 2 | a crowdworker stimulus corpus; the ad ecosystem's own inventory |
Precision of the wide candidate probe: 11 of 29 = 37.9%. Precision of the probe Platforms used, for this question: 10 of 69 = 14.5% — and it also missed one genuine paper, [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)], which uses Google's archive and never says “Ad Library”. Every rejected candidate is printed with its reason on the provenance page, because a residue that lives only in a local script output is a residue nobody looks at.
| Year | Venue | Paper | Archive | Role |
|---|---|---|---|---|
| 2020 | IEEE S&P | [1Edelson, Laura; Lauinger, Tobias; McCoy, Damon (2020): "A Security Analysis of the Facebook Ad Library", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] | Meta Ad Library API + Report | the archive is the object |
| 2020 | TheWebConf | [8Silva, Márcio; Oliveira, Lucas Santos de; Andreou, Athanasios; Melo, Pedro Olmo Stancioli Vaz de; Goga, Oana; Benevenuto, Fabrício (2020): "Facebook Ads Monitor: An Independent Auditing System for Political Ads on Facebook", in: Proceedings of the ACM Web Conference. (DOI)] | Meta Ad Library (Brazil) | archive as comparison target |
| 2021 | IMC | [12Zeng, Eric; Wei, Miranda; Gregersen, Theo; Kohno, Tadayoshi; Roesner, Franziska (2021): "Polls, Clickbait, and Commemorative \$2 Bills: Problematic Political Advertising on News and Media Websites Around the 2020 U.S. Elections", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] | Google political ad archive | 1,000 ads to balance a classifier |
| 2022 | USENIX Sec | [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)] | Meta Ad Library portal, API and snapshot tool | the archive is the object |
| 2023 | IEEE S&P | [5Gkiouzepi, Eleni; Andreou, Athanasios; Goga, Oana; Loiseau, Patrick (2023): "Collaborative Ad Transparency: Promises and Limitations", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] | ad libraries as the critiqued baseline | proposes an alternative |
| 2023 | TheWebConf | [15Coelho, Bruno; Lauinger, Tobias; Edelson, Laura; Goldstein, Ian; McCoy, Damon (2023): "Propaganda Política Pagada: Exploring U.S. Political Facebook Ads en Español", in: Proceedings of the ACM Web Conference. (DOI)] | Meta Ad Library API | archive as corpus, 4.7 M ads |
| 2023 | TheWebConf | [14Capozzi, Arthur; Morales, Gianmarco De Francisci; Mejova, Yelena; Monti, Corrado; Panisson, André (2023): "The Thin Ideology of Populist Advertising on Facebook during the 2019 EU Elections", in: Proceedings of the ACM Web Conference. (DOI)] | Meta Ad Library API | archive as corpus, 44,949 ads |
| 2024 | IMC | [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] | Meta Ad Library API, DSA all-EU scope | the archive is the object |
| 2025 | NDSS | [13Bitaab, Marzieh; Karimi, Alireza; Lyu, Zhuoer; Oest, Adam; Kuchhal, Dhruv; Saad, Muhammad; Ahn, Gail-Joon; Wang, Ruoyu; Bao, Tiffany; Shoshitaishvili, Yan; Doupé, Adam (2025): "ScamMagnifier: Piercing the Veil of Fraudulent Shopping Website Campaigns", in: Proceedings of the Network and Distributed System Security Symposium. (Link)] | Meta Ad Library | secondary corpus for scam ads |
| 2026 | PoPETs | [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] | four platforms' DSA repositories | the repositories are the object |
| 2026 | PoPETs | [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)] | Google Ads Transparency Center via BigQuery | intended ground truth, rejected |
Per venue: TheWebConf 3, IEEE S&P 2, IMC 2, PoPETs 2, USENIX Security 1, NDSS 1. Per year: 2020:2, 2021:1, 2022:1, 2023:3, 2024:1, 2025:1, 2026:2. 2025 and 2026 are provisional venue-years — CCS 2026 and IMC 2026 have not been held, and IEEE S&P 2026 and TheWebConf 2026 abstracts are not in OpenAlex, so those years are under-represented by construction rather than by relevance (corpus).
Eight of the eleven used Meta's archive; three used Google's; none used any of the other eleven DSA repositories. Set against a floor of 180 papers in this corpus whose measured phenomenon is advertising-shaped, the audited set is 10 of them — about 5.6% of advertising measurement in these venues touches an archive.16)
Each figure with the paper's own denominator, and each quote verified against the paper's full text (see ad_archives for the check, which needed a pypdf fallback for 11 of 51 strings).
| Finding | Denominator the paper used |
|---|---|
| 9.7% of ads in the archive carry no disclosure string, $37 M of spend (6% of the total); 68.3% of pages ran at least one undisclosed political ad later detected and added; 15.8% of spend ($98.2 M) unattributable or misattributable; 23% of evaluated disclosure strings non-conforming; 16,160 ads unretrievable via the API [1Edelson, Laura; Lauinger, Tobias; McCoy, Damon (2020): "A Security Analysis of the Facebook Ad Library", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] | 126,013 pages and 3,685,558 ads in the US political Ad Library, May 2018 – June 2019 |
| 55% false-positive rate among US ads Facebook flagged as political; 4.5% false negatives worldwide (116,963 ads), 0.85% in the US against up to 45% elsewhere; 40% of ads detected in under a day [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)] | 33.8 M unique ads observed; 4.2 M political and 29.6 M non-political from all 215,030 pages that ran a political ad, mid-2020 to early 2021 |
| 7.7% moderation recall on undeclared political ads; 60.4% of Meta's own moderations outside Meta's stated criteria; a conservative 1,217 undeclared political ads launched daily; 92 pages moderated 28+ times, 82 still active [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] | all EU ads via the Ad Library API, 16 countries, Aug 2023 – Feb 2024; 29.5 M ads for inference |
| 48% of Facebook and 9% of Instagram ads seen by real users were missing from the platform's DSA repository; 98.9% of YouTube explanations “cite only the main targeting form” [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] | 351 Facebook and 438 Instagram ads matched, from 48,511 donated ad explanations across four platforms |
| Only 34 of 835 ads a classifier judged political had a matching archive entry [8Silva, Márcio; Oliveira, Lucas Santos de; Andreou, Athanasios; Melo, Pedro Olmo Stancioli Vaz de; Goga, Oana; Benevenuto, Fabrício (2020): "Facebook Ads Monitor: An Independent Auditing System for Political Ads on Facebook", in: Proceedings of the ACM Web Conference. (DOI)] | 38,110 ads collected from Brazilian volunteers, 2018 |
| Play Store ads were “entirely missing from the Ad Transparency dataset”; a location-only campaign was listed in the repository with three targeting parameters the advertiser never selected [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)] | 257,820 ads and 378,057 recommendations from 249 accounts on the EU Apple and Google app stores |
| Targeting formula inferred correctly in 17 of 45 controlled campaigns, 65% where 10+ panel users received the ad; 86 of 1,021 ad receptions went to users lacking a targeted attribute [5Gkiouzepi, Eleni; Andreou, Athanasios; Goga, Oana; Loiseau, Patrick (2023): "Collaborative Ad Transparency: Promises and Limitations", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)] | 420 panel users in Brazil, 51,681 Facebook Ads Manager audience-size queries |
| 44,949 ads from 39 parties; populist parties reached 50% more male audiences [14Capozzi, Arthur; Morales, Gianmarco De Francisci; Mejova, Yelena; Monti, Corrado; Panisson, André (2023): "The Thin Ideology of Populist Advertising on Facebook during the 2019 EU Elections", in: Proceedings of the ACM Web Conference. (DOI)] | Meta Ad Library API, 57 party and leader pages, five EU countries, April–May 2019 |
| 1.58% of political ad creatives were in Spanish but 1.90% of spending and 2.25% of impressions [15Coelho, Bruno; Lauinger, Tobias; Edelson, Laura; Goldstein, Ian; McCoy, Damon (2023): "Propaganda Política Pagada: Exploring U.S. Political Facebook Ads en Español", in: Proceedings of the ACM Web Conference. (DOI)] | 4.7 M US political ads from the Facebook Ad Library API, 2020 |
| 67,501 ads (8,836 unique) with political content, 3.9% of the crawl [12Zeng, Eric; Wei, Miranda; Gregersen, Theo; Kohno, Tadayoshi; Roesner, Franziska (2021): "Polls, Clickbait, and Commemorative \$2 Bills: Problematic Political Advertising on News and Media Websites Around the 2020 U.S. Elections", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] | ads crawled from 6,144 mainstream news, 1,344 misinformation and 745 sampled sites, plus 1,000 ads from the Google political ad archive |
| Over 90% of targetable Facebook identities in the US carried at least one data-broker attribute (Australia 81.3%, UK 74.4%) [11Venkatadri, Giridhari; Sapiezynski, Piotr; Redmiles, Elissa M.; Mislove, Alan; Goga, Oana; Mazurek, Michelle L.; Gummadi, Krishna P. (2019): "Auditing Offline Data Brokers via Facebook's Advertising Platform", in: Proceedings of the ACM Web Conference. (DOI)] | the Facebook advertising interface itself, 7 countries — not the archive; included as the contrast case |
Every query, the report script and its unedited output, the full hand-audit with its rejected residue, the quote checks with their fallback modes, and every external source with its fetch date and the ones we rejected are on ad_archives. Corpus-level caveats — the seven-venue scope, the provisional 2025–2026 slice, field stability — are on corpus.
Four limits worth restating here. The corpus is seven security, privacy and measurement venues: political-advertising measurement also lives in ICWSM, CHI, FAccT, Political Communication and the internet-policy journals, none of which are in it, so eleven papers is a count for these seven venues and certainly not for the field. The audited set is small enough that every figure about it is a count, not a rate — do not compute confidence intervals on eleven papers. The archive-by-archive table rests on provider documentation, which is the primary source but also the interested party. And the negative rows — TikTok 0, X 0, LinkedIn 0 — are probe results over full text: a paper that used X's CSV without naming the repository is invisible to them, though at these counts that is unlikely to hide more than one or two papers.
| Method | Verdict | Evidence |
|---|---|---|
| Meta Ad Library API for worldwide political ads | current | 7-year retention, verified 2026-09-08; 8 papers in this corpus |
| Meta Ad Library API for EU political ads | historical from October 2025 | Meta stopped delivering EU political ads on 6 October 2025; the back catalogue remains for 7 years |
| Meta Ad Library API for all EU ads (DSA scope) | current, and the largest under-used surface here | scope added August 2023 [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)]; 1-year window |
| Google political-ads BigQuery public dataset | current outside the EU; EU inflow stopped | Google's own FAQ: “published as a public data set on Google Cloud BigQuery”; EU political ads ended before October 2025 |
| Google Ads Transparency Center for commercial ads | current, web-only, and demonstrably incomplete | [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)] found Play Store ads entirely absent |
| TikTok Commercial Content API | current, EU-only, zero published use in these venues | primary docs 2026-09-08; 0 of 5,855 papers |
| X Ads Repository bulk CSV | current, least gated, zero published use | full commercial-communications CSV, no application, verified 2026-09-08 |
| The EU European repository for political ads | specified, not yet a usable instrument here | Implementing Reg. (EU) 2026/818, 9 April 2026; 0 papers |
| Treating an archive as ground truth | superseded | [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)] rejected it explicitly; [8Silva, Márcio; Oliveira, Lucas Santos de; Andreou, Athanasios; Melo, Pedro Olmo Stancioli Vaz de; Goga, Oana; Benevenuto, Fabrício (2020): "Facebook Ads Monitor: An Independent Auditing System for Political Ads on Facebook", in: Proceedings of the ACM Web Conference. (DOI)], [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)], [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)], [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)] all measure the archive's error instead |
| Two-sided error analysis against the platform's published criteria | current best practice | [2Le Pochat, Victor; Edelson, Laura; Van Goethem, Tom; Joosen, Wouter; McCoy, Damon; Lauinger, Tobias (2022): "An Audit of Facebook's Political Ad Policy Enforcement", in: Proceedings of the USENIX Security Symposium. (Link)], [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] |
| Donation panel as the archive's control | current and rising | [4Benzaamia, Abir; El Fraihi, Asmaa; Abdelaziz, Ines; Goga, Oana (2026): "A Year Under the DSA: Ad Transparency's Uneven Landscape", Proceedings on Privacy Enhancing Technologies 2026(2):517-532. (DOI)], [9Ali, Muhammad; Goetzen, Angelica; Mislove, Alan; Redmiles, Elissa M.; Sapiezynski, Piotr (2023): "Problematic Advertising and its Disparate Exposure on Facebook", in: Proceedings of the USENIX Security Symposium. (Link)], [10Chen, Baiyu; Tag, Benjamin; Xue, Hao; Angus, Daniel; Salim, Flora (2026): "When Ads Become Profiles: Uncovering the Invisible Risk of Web Advertising at Scale with LLMs", in: Proceedings of the ACM Web Conference. (DOI)]; 25 papers mention data donation, 11 in 2025 |
| Own-campaign ground truth | current, small-scale, expensive | [5Gkiouzepi, Eleni; Andreou, Athanasios; Goga, Oana; Loiseau, Patrick (2023): "Collaborative Ad Transparency: Promises and Limitations", in: Proceedings of the IEEE Symposium on Security and Privacy. (DOI)], [7Breuer, David; Becker, Lucas; Hollick, Matthias (2026): "Ad Personalization and Transparency in Mobile Ecosystems: A Comparative Analysis of Google's and Apple's EU App Stores", Proceedings on Privacy Enhancing Technologies 2026(1):604-630. (DOI)], [11Venkatadri, Giridhari; Sapiezynski, Piotr; Redmiles, Elissa M.; Mislove, Alan; Goga, Oana; Mazurek, Michelle L.; Gummadi, Krishna P. (2019): "Auditing Offline Data Brokers via Facebook's Advertising Platform", in: Proceedings of the ACM Web Conference. (DOI)] |
| LLM classification of archive ad text | new: first appearances 2024–2026 | [3Bouchaud, Paul; Liénard, Jean F. (2024): "Beyond the Guidelines: Assessing Meta's Political Ad Moderation in the EU", in: Proceedings of the ACM Internet Measurement Conference. (DOI)] uses an LLM to examine non-moderated ads; [10Chen, Baiyu; Tag, Benjamin; Xue, Hao; Angus, Daniel; Salim, Flora (2026): "When Ads Become Profiles: Uncovering the Invisible Risk of Web Advertising at Scale with LLMs", in: Proceedings of the ACM Web Conference. (DOI)] runs zero-shot Gemini over donated ad sequences, reaching 76.38% gender and 41.60% party accuracy at user level |
| CrowdTangle for adjacent organic content | withdrawn | discontinued 14 August 2024; see Platforms |
An archive study should let a reader reconstruct the population the platform handed you. Report:
curl gets HTTP 403 and the page geo-localises, so it was re-fetched with locale=en_US.curl on 2026-09-08; existence verified from the Mozilla/Check First inventory, not re-rendered.curl and a “Site can't be reached right now” page to a headless browser, so this page makes no claim about it.curl.adobservatory.org does not resolve.detection.phenomenon field and therefore a floor, not a population: a paper that measured advertising without using an ad-shaped word in that field is invisible to it. The field is only about 20% stable run-to-run, so treat 180 as an order of magnitude and 5.6% as a ratio between two candidate sets.