Summary

• The European Commission is consulting on technical guidance for advertising repositories operated by very large online platforms and search engines.
• The work will address search functions, campaign content, audience information, and the targeting criteria available to researchers and regulators.
• The call for evidence closes on 2 December 2026, with final guidelines planned for the second quarter of 2028.

The European Commission is preparing technical guidelines intended to make online advertising databases more useful for investigating scams, misleading campaigns, and potentially unlawful targeting, as existing transparency requirements come under closer regulatory scrutiny.

The European Commission opened a call for evidence on 4 November covering the advertising repositories maintained by very large online platforms and search engines under the Digital Services Act. The consultation will examine how advertisements can be searched, what information is available about their audiences, and whether researchers can access the material needed to examine campaigns properly.

Under Article 39 of the legislation, designated services must maintain publicly accessible repositories recording information about advertisements displayed on their platforms. These include the content of an advertisement, who paid for it, the period during which it appeared, the number of people reached, and the principal criteria used to determine its audience.

The obligations already exist, but the Commission is examining how they should work in practice. A database may formally contain advertising records while offering insufficient search functionality or incomplete information, making it difficult to identify harmful campaigns or examine patterns of advertising activity.

Searchable records provide more than disclosure

Advertising repositories are designed to allow independent examination of activity that would otherwise remain largely within platform systems. Researchers investigating fraudulent investment promotions, for example, may need to identify related advertisements, establish how long they appeared, and determine whether they were directed towards particular groups.

Such investigations become difficult when search results are incomplete or when records cannot be retrieved using relevant information about the advertiser, advertisement content, or campaign period.

The Commission’s proposed guidance will consider how repositories can be made easier to search, how they should describe targeting and audience reach, and how advertising content can be accessed in a form suitable for examination.

These requirements involve more than the presentation of information on a website. Large platforms process substantial volumes of advertisements, many of which are personalised, changed frequently, or displayed only to narrowly defined audiences.

Repositories therefore need systems for collecting, retaining, and retrieving records while ensuring that the information remains consistent with the advertising activity it is supposed to document.

A searchable record may also need to preserve information about the advertisement as it appeared to users, including its wording, visual content, and destination links. Without those details, an investigator may be able to establish that a campaign existed without determining what was actually being promoted.

Targeting information introduces further complexity. Advertising systems may use several categories of information to determine delivery, while the people who ultimately encounter an advertisement may differ from those initially selected by the advertiser.

The Digital Services Act distinguishes the principal targeting criteria from information about the audience reached. Making those fields accessible can help researchers examine whether advertisements were delivered in ways that create particular risks, although aggregate records cannot reveal every individual decision made by a platform’s advertising system.

Previous enforcement exposes practical shortcomings

The Commission has already investigated the usefulness of advertising repositories maintained by major platforms, with enforcement proceedings identifying shortcomings in searchability, access to campaign content, and targeting information.

In December 2025, TikTok offered binding commitments to improve its repository following an investigation under the Digital Services Act. Its agreed measures included providing the content of advertisements as displayed, updating records more quickly, and publishing additional information about targeting and audience reach.

The Commission also required changes to X’s advertising transparency arrangements following a finding of non-compliance. The platform committed to improvements including search functionality and access to advertising information through an application programming interface.

These cases demonstrate how the legal requirement to provide an advertising repository can lead to detailed examination of the system’s technical operation. Maintaining a database is not sufficient if users cannot obtain the information needed to assess advertising activity.

The proposed guidelines could make the Commission’s expectations clearer across designated platforms, reducing uncertainty over what constitutes an effective public advertising repository.

However, the guidance will not replace the existing legislation. Article 39 already establishes the relevant obligations, while the Commission is developing more detailed expectations concerning their technical implementation.

Advertising businesses face greater scrutiny

Better access to advertising records could have consequences beyond regulatory investigations. Advertisers, agencies, and technology suppliers may find that campaign activity becomes easier for competitors, consumer organisations, journalists, and researchers to examine.

This includes campaigns that are targeted narrowly enough to remain largely invisible to people outside their intended audience. Public repositories can provide a route to discovering such advertisements without requiring investigators to reproduce the targeting conditions used to deliver them.

Advertising transparency is also relevant to consumer protection, particularly where fraudulent promotions impersonate legitimate businesses or lead users towards websites designed to obtain payments or personal information.

Researchers may use historical records to establish whether similar advertisements appeared repeatedly, whether multiple accounts promoted related material, and how particular campaigns changed over time.

More consistent data could also support independent monitoring services, although the commercial possibilities will depend on the methods of access eventually required and the reliability of the information supplied.

For platforms, implementation may involve changes to advertising data systems, retention arrangements, search interfaces, and the technical processes used to supply records. These are operational requirements rather than simply additional disclosures in advertising policies.

Providers will also need to balance the publication of useful aggregate information with the protection of personal data, particularly when audience reporting concerns relatively small groups.

Because advertising systems differ considerably between services, a common framework must establish sufficiently clear requirements without assuming that every platform collects or structures its information in the same way.

Guidelines are still two years away

The initial call for evidence closes on 2 December 2026. The Commission will then conduct a targeted public consultation in 2027, inviting input from researchers, civil society, advertising industry representatives, and the providers of designated platforms and search engines.

Publication of the final guidelines is planned for the second quarter of 2028. The timetable leaves considerable scope for discussion of technical design and implementation, although existing legal obligations continue to apply throughout the consultation process.

The resulting guidance is intended to support supervision and enforcement by clarifying how advertising repositories can satisfy the requirements already established under the Digital Services Act.

Its effectiveness will ultimately depend on whether researchers and regulators can retrieve sufficiently complete, timely, and understandable information to investigate online advertising practices without relying entirely on the platforms whose activity they are examining.