1. Introduction

A dominant ecosystem is a business environment in which one undertaking controls or strongly influences several connected products, services, platforms, technologies, data sources, or distribution channels. Examples can include a digital operating system connected with an app store, search engine, advertising service, browser, cloud service, payment system, or online marketplace.

Competition law does not generally prohibit a company from becoming dominant. The legal concern arises when dominance is used in a way that restricts competition, excludes rivals, exploits dependent businesses, or prevents markets from remaining contestable.

Under Article 102 TFEU, for example, abusive conduct by a dominant undertaking is prohibited. The European Commission's September 2026 exclusionary-abuse guidelines emphasise greater legal certainty and consistency in assessing conduct by dominant firms.

For dominant ecosystems, accountability therefore means that the ecosystem operator may need to demonstrate that important decisions concerning access, ranking, interoperability, data, pricing, and treatment of competitors are objectively justifiable and consistent with competition rules.

2. Meaning of Accountability in Competition Law

Accountability standards are the legal and regulatory mechanisms used to ensure that a dominant undertaking can be examined and, where necessary, required to justify or modify conduct that affects competition.

Important standards include:

1. Transparency
2. Non-discrimination
3. Fair access
4. Objective justification
5. Interoperability
6. Data governance
7. Procedural fairness
8. Internal compliance controls
9. Monitoring and reporting
10. Effective remedies

The precise obligation depends on the jurisdiction and the legal theory of harm.

3. Identification of Dominance

The first question is normally whether the undertaking possesses substantial market power.

Authorities may consider:

• market share;
• barriers to entry;
• network effects;
• switching costs;
• control over infrastructure;
• access to important data;
• vertical integration;
• economies of scale;
• ecosystem lock-in;
• technological advantages;
• access to customers; and
• the strength of existing competitors.

A company can therefore have significant competitive importance even where its position is not explained solely by traditional market-share analysis.

The EU's Digital Markets Act provides a particularly important example of ecosystem accountability: the Commission has designated companies including Alphabet, Amazon, Apple, ByteDance, Meta and Microsoft as gatekeepers for specified core platform services.

4. Self-Preferencing

One of the principal accountability issues is self-preferencing.

This occurs where an ecosystem operator gives its own products or services preferential treatment compared with competing third-party services.

Examples could include:

• giving its own shopping service superior search placement;
• favouring its own financial service;
• ranking its own applications more prominently;
• giving its own advertising products better access to data;
• using proprietary infrastructure to advantage affiliated services.

The central competition question is whether the conduct disadvantages rivals because of the ecosystem operator's control over an important platform.

In July 2026, the European Commission announced a €460 million DMA fine concerning Google's treatment of its own services in Google Search, finding that Google had given preferential treatment to its own services in areas including shopping, hotels, transport and sports results.

5. Access and Non-Discrimination

A dominant ecosystem can create competitive problems by controlling access to an important facility.

Accountability may require:

• clearly defined access conditions;
• transparent eligibility requirements;
• reasonable technical standards;
• non-discriminatory treatment;
• predictable procedures;
• explanations for refusals;
• appeal mechanisms.

This becomes particularly important where competitors depend upon the ecosystem to reach consumers.

The essential-facilities doctrine is relevant in some circumstances, although competition law generally does not impose a universal duty on every dominant company to share its assets.

6. Interoperability

Interoperability allows competing products or services to work with an ecosystem.

Important areas include:

• messaging;
• operating systems;
• cloud services;
• payment systems;
• APIs;
• hardware functionality;
• artificial-intelligence services;
• data portability.

The European Commission's 2026 DMA measures concerning Google illustrate this direction. The Commission issued binding measures addressing interoperability between competing AI services and Android functionality.

The accountability principle is that control over technical architecture should not automatically become a mechanism for excluding competing services.

7. Data Accountability

Data can reinforce ecosystem dominance.

A dominant platform may possess:

• search data;
• transaction data;
• advertising data;
• consumer behaviour information;
• business-user data;
• location information;
• technical performance data.

Competition concerns can arise when the dominant undertaking uses data obtained from dependent businesses to compete against those same businesses.

The EU's DMA framework increasingly addresses data access. In July 2026, the Commission adopted measures requiring Google to facilitate access by eligible search competitors to anonymised Google Search data under fair, reasonable and non-discriminatory terms.

8. Ranking Accountability

Ranking systems are particularly important in ecosystems because algorithms can determine commercial visibility.

Accountability may involve:

• transparent ranking principles;
• consistent application of ranking rules;
• safeguards against discriminatory treatment;
• explanation of major changes;
• auditing mechanisms;
• protection against manipulation.

The UK's Competition and Markets Authority has imposed fair-ranking and data-portability conduct requirements on Google in relation to its general search services under the UK's digital-markets regime.

9. Platform Steering Restrictions

A dominant ecosystem may prevent businesses from directing customers toward alternative channels.

For example, a platform could restrict an app developer from telling consumers that a product is available more cheaply elsewhere.

Competition law may examine whether such restrictions:

• increase platform dependency;
• raise transaction costs;
• prevent price competition;
• protect the platform's commissions;
• restrict alternative distribution channels.

The European Commission's 2026 DMA enforcement against Google included a €430 million fine concerning restrictions on businesses directing consumers to alternative purchasing channels through Google Play.

10. Ecosystem Lock-In

Lock-in occurs when consumers or businesses face substantial difficulty moving away from an ecosystem.

Sources of lock-in may include:

• proprietary data formats;
• high switching costs;
• loss of historical data;
• incompatible software;
• exclusive functionality;
• contractual restrictions;
• technical restrictions;
• network effects.

Competition law is particularly interested in whether a dominant undertaking deliberately creates or strengthens barriers that prevent competitors from attracting users.

11. Accountability Through Internal Compliance

A sophisticated dominant ecosystem should maintain competition-law compliance systems.

These may include:

A. Competition compliance officer

Responsible for identifying potentially problematic practices.

B. Conduct review committees

Review major changes to:

• ranking;
• access;
• pricing;
• APIs;
• data policies;
• interoperability;
• platform rules.

C. Written decision records

Important commercial decisions should have documented reasons.

D. Competition impact assessments

Major ecosystem changes can be assessed before implementation.

E. Independent audits

External or independent reviews can examine whether commitments are being followed.

F. Complaint mechanisms

Business users and competitors should have channels for raising concerns.

12. Six Important Case Laws

Case 1 — Google Shopping

Google Search (Shopping), Case AT.39740, European Commission

The European Commission found that Google had abused its dominant position in general search by giving prominent placement to its own comparison-shopping service while applying less favourable treatment to competing comparison-shopping services.

Competition principle

A dominant platform controlling an important gateway must be careful when it uses that gateway to favour its own downstream service.

Accountability lesson

Ranking and display decisions should be capable of objective scrutiny rather than being used as an opaque mechanism for disadvantaging rivals.

Case 2 — Google Android

Google Android, Case AT.40099, European Commission

The case concerned Google's practices involving the Android mobile ecosystem, including restrictions associated with device manufacturers and the distribution of Google services.

The Commission concluded that certain practices strengthened Google's position in general search and restricted competing opportunities. The Commission's decision specifically discussed how restrictions on Android forks could raise barriers for competing search services.

Competition principle

Control of an operating-system ecosystem can have consequences beyond the operating-system market itself.

Accountability lesson

A dominant ecosystem should consider the competitive effects of contractual and technical restrictions across connected markets.

Case 3 — Microsoft

Microsoft Corp. v Commission, Case T-201/04

The EU Microsoft litigation involved Microsoft's conduct concerning interoperability information and the tying of Windows Media Player with Windows.

The case became an important reference point for:

• interoperability;
• tying;
• refusal to supply;
• technological integration;
• remedies involving dominant platforms.

Competition principle

A dominant technology company cannot necessarily use control over one technological layer to foreclose competition in adjacent markets.

Accountability lesson

Technical decisions can have competition-law consequences when the undertaking controls an important technological gateway.

Case 4 — Intel

Intel Corp. v European Commission, Case C-413/14 P

The Intel litigation concerned rebates granted by Intel to major computer manufacturers and a retailer.

The EU courts developed important principles concerning the assessment of exclusionary rebate practices, including consideration of whether conduct is capable of producing anticompetitive foreclosure effects.

Competition principle

The assessment of dominant-firm conduct requires careful analysis of the actual competitive effects and economic circumstances.

Accountability lesson

Dominant undertakings should retain adequate evidence demonstrating the competitive rationale for major commercial practices.

Case 5 — IMS Health

IMS Health GmbH & Co. OHG v NDC Health GmbH & Co KG, Case C-418/01

The case concerned access to a commercially important data structure protected by intellectual-property rights.

The Court established demanding conditions under which refusal to license intellectual property could constitute an abuse of dominance.

Competition principle

A dominant company does not automatically have to license intellectual property merely because competitors want access.

However, exceptional circumstances can justify intervention.

Accountability lesson

Access decisions should be supported by objective criteria, especially where competitors depend upon an important technological or informational resource.

Case 6 — Bronner

Oscar Bronner GmbH & Co. KG v Mediaprint, Case C-7/97

The case concerned access to a newspaper home-delivery system.

The Court applied a strict test to determine when refusal of access to infrastructure can constitute an abuse.

Competition principle

Competition law generally does not require dominant companies to share every facility with competitors.

Intervention requires exceptional circumstances.

Accountability lesson

A request for ecosystem access should be assessed using clear legal criteria rather than assuming that dominance automatically creates an unlimited sharing obligation.

13. Additional Important Case — United Brands

United Brands v Commission, Case 27/76

United Brands remains a foundational EU dominance case.

The Court considered issues involving:

• market power;
• commercial relationships;
• discriminatory treatment;
• exclusionary conduct;
• dependence on a dominant undertaking.

Ecosystem relevance

Although the case predates modern digital ecosystems, its broader principles remain useful for understanding how a dominant undertaking's commercial behaviour toward trading partners can be scrutinised.

14. Dominant Ecosystems and the Digital Markets Act

Traditional competition law generally operates through an ex-post model: authorities investigate conduct and determine whether it constitutes an abuse.

The Digital Markets Act adds an important ex-ante approach for designated gatekeepers.

The framework establishes obligations concerning areas such as:

• self-preferencing;
• interoperability;
• data access;
• switching;
• steering;
• business-user rights;
• platform neutrality.

This is significant because regulators do not always need to wait for a lengthy conventional abuse-of-dominance investigation.

The European Commission currently lists Alphabet, Amazon, Apple, Booking, ByteDance, Meta and Microsoft among designated gatekeepers, with particular core platform services identified for each company.

15. Core Accountability Standards

16. Role of Competition Authorities

Competition authorities can investigate:

• exclusionary agreements;
• discriminatory access;
• tying and bundling;
• loyalty-inducing rebates;
• refusal to supply;
• self-preferencing;
• predatory pricing;
• interoperability restrictions;
• data exploitation;
• discriminatory ranking;
• anti-steering provisions;
• acquisitions that reinforce ecosystem power.

Possible remedies include:

• behavioural commitments;
• access obligations;
• interoperability requirements;
• data-sharing requirements;
• changes to contractual terms;
• monitoring trustees;
• reporting obligations;
• structural remedies in appropriate cases;
• monetary penalties.

17. Dominant Ecosystems and Consumer Welfare

The ultimate competition-law concern is not simply the size of an ecosystem.

A large ecosystem can provide substantial benefits through:

• innovation;
• lower costs;
• integrated services;
• convenience;
• security;
• network effects.

The legal question is whether conduct by the dominant undertaking protects those legitimate efficiencies or instead suppresses competitive pressure.

Therefore, regulators normally need to distinguish:

Competition on the merits

from

exclusionary conduct made possible by ecosystem control.

18. Key Legal Test

A simplified analytical framework is:

Step 1 — Define the relevant market

↓

Step 2 — Establish dominance or gatekeeper status

↓

Step 3 — Identify the conduct

↓

Step 4 — Determine how the conduct affects competitors, business users and consumers

↓

Step 5 — Examine foreclosure or exploitation effects

↓

Step 6 — Consider objective justification and efficiencies

↓

Step 7 — Assess proportionality and available remedies

This framework is particularly useful for examining digital ecosystems where several connected markets operate simultaneously.

19. Major Challenges

1. Multi-market dominance

An ecosystem may have power in several connected markets rather than one clearly isolated market.

2. Network effects

More users can make the ecosystem more valuable, making entry increasingly difficult.

3. Data advantages

Large quantities of data can improve products and reinforce existing market power.

4. Algorithmic opacity

Competitors may not know why their ranking or access has changed.

5. Rapid innovation

Competition authorities must distinguish genuine technological innovation from technical restrictions designed to exclude rivals.

6. Ecosystem-wide effects

Conduct in one service can strengthen dominance in another.

20. Conclusion

Accountability standards for dominant ecosystems are designed to ensure that substantial market power is exercised within competition-law boundaries.

The most important principles are:

1. dominance itself is not unlawful;
2. abuse of dominance can be unlawful;
3. ecosystem control can extend competitive power into neighbouring markets;
4. self-preferencing can receive regulatory scrutiny;
5. access and interoperability can become important competition issues;
6. data can be both an economic asset and a source of competitive advantage;
7. ranking and platform rules should not arbitrarily discriminate against rivals;
8. dominant firms should maintain strong competition-compliance systems;
9. regulators can use both traditional antitrust rules and newer ex-ante digital-market regimes; and
10. remedies increasingly focus on restoring contestability rather than merely imposing penalties.