Competition Law and Cross-Sector Platform Domination

1. Introduction

Cross-sector platform domination describes a situation in which a powerful digital platform uses its position, assets, or advantages in one market to strengthen or extend its position into other markets. Modern digital platforms rarely operate in only one line of business. A single ecosystem may include search, advertising, social networking, mobile operating systems, app distribution, e-commerce, payments, cloud computing, streaming, artificial intelligence, and other services.

Competition law does not prohibit a company merely because it becomes large or successfully operates across several sectors. The central legal question is whether the company uses market power in a way that restricts competition through practices such as self-preferencing, tying, discriminatory access, exclusionary agreements, data leveraging, interoperability restrictions, or other forms of foreclosure.

The subject is particularly important because platform markets often involve network effects, economies of scale, extensive data collection, ecosystem integration, and relatively high switching costs. These characteristics can make market power obtained in one sector useful for expansion into another.

2. Meaning of Cross-Sector Platform Domination

Cross-sector domination can arise where a platform has substantial power in Market A and uses advantages associated with that position to obtain or protect power in Market B, C, or D.

For example:

Search → Shopping → Advertising → Mobile services

or:

Operating system → App store → Payments → Streaming

or:

Social network → Advertising → Messaging → Digital commerce

The competitive concern is therefore not simply the size of the overall corporation. Competition authorities examine the connection between different markets and whether conduct in one market changes competitive conditions in another.

This is commonly discussed through the competition-law concept of leveraging.

A dominant position in one market does not automatically make expansion unlawful. Problems arise where the method of expansion departs from competition on the merits and is capable of excluding competitors or weakening effective competition.

3. Relevant Market and Dominance

The first major task is normally identifying the relevant markets.

A competition authority may separately examine:

• general online search;
• comparison-shopping services;
• mobile operating systems;
• app distribution;
• social networking;
• online advertising;
• payment processing;
• online marketplaces;
• cloud infrastructure;
• messaging;
• video distribution.

After defining the relevant market, the authority examines whether the platform possesses substantial or dominant market power.

Important considerations include market shares, network effects, access to data, switching costs, economies of scale and scope, control of essential distribution channels, barriers to entry, multi-homing possibilities, user dependence, and the availability of realistic substitutes.

A platform can therefore be dominant in one market without being dominant throughout its entire ecosystem.

4. Leveraging Market Power Across Sectors

Leveraging occurs where advantages derived from one market are used to influence competition in another.

Suppose Platform P controls a major operating system. It also introduces its own payment service. If it merely competes by offering a better payment service, expansion is ordinarily part of normal competition.

The position becomes more difficult where Platform P makes access to its operating system conditional upon using its payment system, blocks rival payment providers, gives its own service technically privileged access, or imposes restrictions that materially disadvantage competing providers.

Competition law therefore distinguishes between:

legitimate ecosystem expansion

and

anticompetitive leveraging of market power.

5. Self-Preferencing

Self-preferencing occurs where a platform controlling an important gateway gives preferential treatment to its own downstream service.

This can include:

• preferential ranking;
• superior placement;
• exclusive access to particular technical functions;
• preferential default settings;
• preferential access to customer information;
• discriminatory fees;
• better interoperability for the platform's own products.

Self-preferencing is not automatically unlawful in every jurisdiction or factual setting. The legal assessment generally considers the platform's market power, the nature of the differential treatment, and its capacity to restrict competition.

The Google Shopping litigation is particularly important because EU courts considered Google's treatment of its own comparison-shopping service relative to competing comparison-shopping services.

6. Tying and Bundling

Cross-sector expansion may also occur through tying.

A tying product is a product in which a company possesses substantial market power, while the tied product is another product or service that users are required or strongly induced to obtain together with it.

For example:

Operating system + browser

Operating system + media player

Mobile ecosystem + app store

App store + payment mechanism

Tying can create efficiencies. Integrated products can reduce transaction costs and improve functionality. Competition concerns become stronger when tying makes it significantly harder for competing suppliers in the adjacent market to reach customers.

7. Data as a Cross-Market Advantage

Digital platforms may obtain data from several different services.

For example, a platform could potentially receive information from social networking, websites, mobile applications, advertising services, marketplaces, or other ecosystem services.

Combining datasets may improve personalization and advertising efficiency. At the same time, extensive cross-service data combination can strengthen entry barriers where competitors cannot realistically reproduce the information advantage.

The European Court of Justice's Meta Platforms v Bundeskartellamt judgment is especially significant here. It concerned the relationship between dominance, competition-law enforcement and the processing of personal data. The Court confirmed that a competition authority assessing abuse of dominance can, subject to cooperation requirements, consider compliance with data-protection rules where relevant to the competition assessment.

8. Network Effects and Ecosystem Entrenchment

Platforms often benefit from network effects.

A direct network effect exists where a service becomes more useful as additional users join it. An indirect network effect may arise when growth on one side of a platform attracts participants on another side.

For example:

more consumers → more sellers

more sellers → more consumers

more app users → more developers

more developers → more useful applications

more applications → more users

Once several connected network effects operate across an ecosystem, competitors may have difficulty challenging the platform on only one component.

Competition authorities therefore increasingly examine ecosystems rather than treating every digital product as completely isolated.

Important Case Laws

9. Google and Alphabet v European Commission (Google Shopping) — Case C-48/22 P

This is one of the clearest cases concerning cross-market leveraging by a digital platform.

Google held a dominant position in general online search in the relevant markets. The European Commission found that Google gave its own comparison-shopping service preferential treatment in general search results while competing comparison-shopping services were treated less favourably.

The dispute therefore involved the relationship between two connected markets:

general search → comparison shopping.

The General Court largely upheld the Commission's decision, and on 10 September 2024 the Court of Justice dismissed Google and Alphabet's appeal. The Court described the dispute expressly in terms of leveraging and the preferential display of Google's own specialised search results.

The case demonstrates that dominance in one platform market can create competition-law problems where the platform uses the characteristics of that dominant service to favour its activities in an adjacent market.

Principle: Cross-market expansion itself is lawful, but preferential treatment by a dominant gateway can constitute abuse where the relevant legal conditions and anticompetitive potential are established.

10. Google Android — Google and Alphabet v Commission, Case T-604/18

The Android litigation concerned Google's practices relating to the Android mobile ecosystem.

The Commission's case addressed contractual arrangements concerning Android device manufacturers and mobile network operators, including requirements associated with Google's search and browser applications and restrictions relating to competing versions of Android.

The General Court's 2022 judgment largely confirmed the Commission's infringement findings while modifying aspects of the decision and fine.

For cross-sector domination, the importance of the case lies in the interaction between:

mobile operating systems → app distribution → browsers → search services.

The case illustrates how contractual arrangements surrounding one part of a digital ecosystem can influence competition in another.

Principle: Competition authorities may examine an integrated platform ecosystem where contractual or technical arrangements surrounding one service can protect or expand market power in connected services.

11. Microsoft Corp. v European Commission — Case T-201/04

The Microsoft case is a foundational authority on technological ecosystems and leveraging.

The dispute involved, among other matters, Microsoft's Windows operating system and Windows Media Player, as well as interoperability information relating to work-group server operating systems.

The European Commission concluded that particular practices constituted abuse of Microsoft's dominant position. The General Court substantially upheld the Commission's findings.

The case is relevant to cross-sector platform domination because control of an operating-system platform can provide powerful distribution advantages to products supplied in neighbouring software markets.

Principle: A dominant technological platform cannot necessarily use integration or restrictions on interoperability to exclude competition in adjacent markets merely because the products form part of the same ecosystem.

12. Microsoft Corp. v Commission — Case T-167/08

This later Microsoft litigation concerned compliance with obligations arising from the earlier competition proceedings, particularly regarding interoperability information and the terms on which it was made available.

Its broader significance concerns access to interoperability information in markets characterised by powerful platform effects.

Interoperability can be crucial for competitors attempting to build products capable of functioning effectively with a dominant ecosystem.

Principle: Competition concerns may continue beyond an initial infringement where access conditions to interoperability information affect whether competing products can operate effectively alongside a dominant platform.

13. Meta Platforms Inc and Others v Bundeskartellamt — Case C-252/21

This judgment of the Court of Justice, delivered on 4 July 2023, is important for understanding how competition law interacts with data-driven platform ecosystems.

The proceedings arose from the German competition authority's action concerning Meta/Facebook and the processing of user data.

The case connected:

social networking → user data → online advertising → services across the wider digital ecosystem.

The Court addressed whether a national competition authority could consider compliance with the GDPR while investigating an alleged abuse of dominant position. It held, in substance, that such considerations can be relevant, while requiring appropriate cooperation with the competent data-protection authorities.

The underlying German proceedings ultimately concluded after implementation measures; the Bundeskartellamt stated in October 2024 that the measures were sufficient to close the case.

Principle: In digital markets, competition assessment can intersect with data protection because access to and processing of data may be closely connected with the exercise of market power.

14. Google Search (Shopping) — Case T-612/17

Before the Court of Justice's 2024 appellate judgment, the General Court considered Google's challenge to the European Commission's Google Shopping decision.

The General Court largely dismissed Google's action and upheld the core finding relating to preferential treatment of Google's own comparison-shopping service.

The case is important because it developed the legal analysis subsequently considered by the Court of Justice in Case C-48/22 P.

The Court of Justice ultimately upheld the essential result in September 2024, confirming the significance of leveraging and self-preferencing analysis in this setting.

Principle: A dominant general platform's control over user traffic can become competitively significant where its treatment of downstream services systematically favours its own offering.

15. Microsoft Corp. v Commission — Case T-286/09

This proceeding also developed out of Microsoft's compliance obligations concerning interoperability information.

Although arising from the wider Microsoft enforcement history rather than a modern multi-sided platform case, it remains relevant to cross-sector ecosystem analysis because technical interoperability can determine whether competitors can participate effectively in neighbouring technology markets.

Principle: Control over technical interfaces and interoperability can function as a strategic competitive asset, and restrictions concerning that access may attract scrutiny when held by a dominant undertaking.

16. Slovak Telekom v European Commission — Case C-165/19 P

Although this case arose in telecommunications rather than a modern consumer digital platform, it is important for understanding infrastructure-based leveraging and refusal-of-access principles.

The dispute concerned access to a dominant telecommunications operator's local network infrastructure and practices affecting competing providers.

Its significance for platform markets lies in the general principle that control over infrastructure used by downstream competitors can create opportunities for exclusion.

Digital analogies can arise with operating systems, APIs, app distribution systems, marketplaces, technical interfaces, and other gateway infrastructure, although the precise legal test depends on the conduct and circumstances.

Principle: Dominant control of upstream infrastructure can have downstream competitive consequences, but the applicable legal test depends on whether the conduct involves outright refusal, unfair access conditions, margin squeeze, or another form of exclusion.

17. Main Theories of Harm

Cross-sector platform domination can therefore involve several competition theories.

A. Leveraging

Market power in Market A is used to obtain or strengthen a position in Market B.

B. Self-Preferencing

The platform gives its own downstream service advantages unavailable to competing businesses.

C. Tying

Access to one important service is linked to adoption of another service.

D. Bundling

Several services are offered together in a manner that can make independent competition more difficult.

E. Interoperability Restrictions

Competitors are denied or disadvantaged in obtaining technical compatibility with the dominant ecosystem.

F. Data Advantages

Data obtained from one service can strengthen the platform's competitive position in another service.

G. Default Settings

A platform's service may become the default on devices or software, potentially affecting user choice and rival distribution.

H. Discriminatory Access

A platform controlling a gateway may impose less favourable technical or commercial conditions on businesses competing with its own products.

18. Ecosystem Theory of Competition

Traditional competition law often analyses individual product markets separately.

Digital platforms make this more complicated because products can be interconnected.

Consider an ecosystem containing:

Operating System → App Store → Browser → Search → Advertising → Payment → Cloud

Each product may constitute a separate market, but competitive advantages can move through the ecosystem.

Control of the operating system may influence app distribution.

Control of app distribution may influence payment services.

Control of search may influence shopping services.

Control of user data may influence advertising.

Consequently, authorities may need to examine both individual relevant markets and the economic connections between them.

19. Foreclosure Effects

Foreclosure means that competitors' ability to compete effectively is materially restricted.

Potential mechanisms include:

• reduced visibility;
• loss of access to users;
• increased distribution costs;
• technical incompatibility;
• reduced access to important inputs;
• exclusion from defaults;
• discriminatory ranking;
• reduced access to data.

Competition law generally focuses on the capacity of conduct to restrict effective competition rather than simply protecting an individual competitor from aggressive but legitimate competition.

The Court of Justice's Google Shopping judgment expressly addressed the potential anticompetitive effects and capability of foreclosure associated with the conduct under examination.

20. Consumer Harm

Cross-sector platform dominance can potentially affect consumers through higher prices, reduced innovation, diminished quality, reduced privacy or choice, and fewer viable alternative platforms.

However, consumer harm is not assumed simply because a large platform enters several sectors.

Cross-sector integration can also produce efficiencies such as:

• seamless interoperability;
• lower transaction costs;
• integrated security;
• improved functionality;
• reduced prices;
• convenient single-account systems;
• faster innovation.

Competition analysis therefore has to distinguish efficient integration from exclusionary conduct.

21. Role of Article 102 TFEU

Within EU competition law, Article 102 TFEU is particularly important.

It prohibits the abuse of a dominant position within the internal market, or a substantial part of it, where trade between Member States may be affected.

Dominance itself is not prohibited.

Accordingly:

Dominance + legitimate competition = generally lawful

while:

Dominance + abusive exclusionary or exploitative conduct = potentially unlawful

This distinction is essential when analysing cross-sector platforms.

22. Merger Control and Cross-Sector Expansion

Cross-sector domination can also arise through acquisitions rather than unilateral conduct.

A platform might acquire businesses operating in:

• artificial intelligence;
• advertising technology;
• payments;
• logistics;
• cloud computing;
• social networking;
• gaming;
• e-commerce;
• digital health;
• data analytics.

Merger authorities may investigate whether an acquisition removes an important potential competitor, gives the platform control over strategically important inputs, strengthens ecosystem effects, facilitates foreclosure, or entrenches existing market power.

This is different from abuse-of-dominance enforcement because merger control usually examines the likely competitive consequences of a transaction before or around its implementation rather than punishing dominance itself.

23. Remedies

Where unlawful cross-sector leveraging is established, remedies can include behavioural and, in appropriate legal systems and circumstances, structural measures.

Possible behavioural remedies include:

• non-discriminatory access requirements;
• interoperability obligations;
• changes to default arrangements;
• restrictions on tying;
• equal-treatment requirements;
• changes to contractual terms;
• access to necessary technical information.

Authorities may also impose fines where the governing legislation permits them.

The appropriate remedy should address the identified competition problem without unnecessarily eliminating efficiencies arising from legitimate integration.

24. Overall Legal Position

Cross-sector platform domination represents one of the major challenges of modern competition law because digital companies can operate interconnected services whose competitive significance cannot always be understood by examining each product independently.

The major cases show several recurring principles.

First, being dominant or operating a large ecosystem is not itself unlawful.

Second, competition law becomes particularly important when dominance in one market is used through exclusionary conduct to influence another market.

Third, self-preferencing, tying, interoperability restrictions, discriminatory access, defaults, and data practices can provide mechanisms through which cross-market leveraging occurs.

Fourth, the authority still needs an evidence-based assessment of the relevant markets, dominance, the particular conduct, its context and its actual or potential effects.

Finally, cases such as Google Shopping, Google Android, Microsoft, Meta Platforms v Bundeskartellamt, and Slovak Telekom demonstrate that competition law increasingly has to examine not only isolated products but also relationships between infrastructure, data, distribution channels, and neighbouring digital markets.

Thus, the central competition-law question is not simply whether a platform dominates several sectors. It is whether market power in one part of an ecosystem is being used in a legally abusive way to distort competition in another part of that ecosystem.