# Market Power and Gatekeepers: Complements or Substitutes?*

Florence Thépot**

**ABSTRACT:** Although they are distinctive instruments, Article 102 TFEU and the Digital Markets Act (DMA) commonly target undertakings with high degrees of economic power. In Article 102 TFEU, market power assessment, including market definition has been considerably challenged by specific features of digital markets. With the use of thresholds-based presumptions to designate gatekeepers, the DMA thus purportedly moves away from Article 102 TFEU analytics. This article questions the extent to which market power and gatekeeper powers are substitutes, or complements, regarding the analytical tools used, and regarding the purposes to which they contribute. While market power methodology moves away from quantitative methods, for greater accuracy, the DMA reinjects a great dose of quantitative-based tools. Yet, as the DMA decisional practice shows, both analyses comprise, with varied intensity, an assessment of qualitative factors, revolving around barriers to entry. In addition, issues of boundaries' delineation feature in both methodologies. The tools on which they rely are substitutes, but with complementary scope and outcomes. Finally, market and gatekeeper powers may be both substitutes in how they contribute to contestability of markets, albeit with a complementary twist: respectively with access to a user base for the DMA, and in a relevant market for Article 102 TFEU.

**KEYWORDS:** Digital Markets Act; gatekeepers; market power; market definition; digital markets

<footnote>* Date of reception: 14.01.2025; Date of acceptance: 05.02.2025.</footnote>

<footnote>DOI: https://doi.org/10.34632/mclawreview.2025.17736.</footnote>

<footnote>** University of Strasbourg, France. The author wishes to thank the editors for the support in the publication process, and the anonymous reviewer for their comments.</footnote>
## Introduction

The concept of market power is of central importance to EU competition law, as closely linked to anti-competitive effects and theories of harm that justify intervention. Degrees of market power often determine whether a given behaviour, agreement, or transaction must be scrutinised in the first place under Articles 101¹ and 102 of the Treaty on the Functioning of the European Union (“TFEU”) and under the EU Merger Regulation (“EUMR”).<fnref n="2" />

The finding of dominance, that is, of a significant amount of market power,<fnref n="3" /> is indeed a pre-condition for the application of Article 102 TFEU. At the turn of the twenty-first century, the emergence of digital platforms, and their specific economic characteristics, put to the test the concept of market power and its methodologies – particularly market definition, used in enforcement.<fnref n="4" /> Notwithstanding the intense enforcement activity illustrated by numerous high profile cases involving big tech companies,<fnref n="5" /> many jurisdictions took initiatives to tackle the entrenched position of large digital platforms, ranging from reforms of competition law, to rule-based

<footnote n="1">¹ Article 101 TFEU [2010] OJ C83/01 exempts agreements of minor importance (with exceptions), under various Block Exemption Regulations; Article 101(3) automatically applies to agreements between parties without market power (provided the absence of hard core restrictions), and the existence of market power is an important factor in the individual assessment of agreements that are above market-share thresholds.</footnote>

<footnote n="2">² Regulation 139/2004 on the Control of Concentrations between Undertakings OJ L24/1, “EUMR”: Merger control’s intervention also rests (mostly) on an analysis of market power with the “significant impediment of effective competition”.</footnote>

<footnote n="3">³ Judgment of the Court of 14 February 1978, *United Brands Company and United Brands Contingentaaal v. Commission*, C- 27/76, ECR 207, paragraph 65; Judgment of the Court of 13 February 1979, *Hoffmann-La Roche & Co. v. Commission*, C-85/76, ECR 461, paragraph 38.</footnote>

<footnote n="4">⁴ OECD (2022), “The Evolving Concept of Market Power in the Digital Economy”, DAF/ COMP(2022)5 OECD Roundtables on Competition Policy Papers, No. 278, OECD Publishing, Paris, I. Lianos, B. Carballa-Smichowski, “A coat of many colours – New concepts and metrics of economic power in competition law and economics”, *Journal of Competition Law & Economics* 18, no. 4 (2022): 795-831, F. Thépot, “Market power in online search and social-networking: A matter of two-sided markets”, *World Competition Law and Economics Review*, Kluwer Law International 36 (2013): 195-221.</footnote>

<footnote n="5">⁵ Just to name a few EU cases: Commission Decision of 27 June, AT.39740, *Google Search (Shopping) OJ C9/11*; Judgement of the Court of 10 November 2021, *Google and Alphabet v. Commission*, T-612/17, ECLI:EU:T:2021:763; Judgement of the Court of 10 September 2024, *Google and Alphabet v. Commission (Google Shopping)*, C-48/22 P, ECLI:EU:C:2024:726. Commission Decisions of 20 December 2022, AT.40462, *Amazon Marketplace* and AT.40703, *Amazon Buy Box*. Commission Decision of 4 March 2024, AT.40437, *Apple – App Store Practices (music streaming)*.</footnote>
legislation.<fnref n="6" /> In the EU, the Digital Markets Act (The “DMA”), introduced in 2022 to complement competition law provisions, set obligations to large digital platforms identified as “Gatekeepers” of “Core Platform Services” (“CPS”), to enhance contestability and fairness in the digital sector.<fnref n="7" /> The DMA clarifies its articulation with competition law provisions: Article 102 TFEU is based on an *ex post* individualised assessment of market positions and behaviours, while the DMA imposes, *ex ante*, uniform obligations to those subject to it, without the identification of harm.<fnref n="8" /> In addition, the DMA only applies to the digital sector, makes no mention of “market power”, and distances itself from dominance.<fnref n="9" />

Although they are distinctive instruments, Article 102 TFEU and the DMA commonly target undertakings with high degrees of economic power.<fnref n="10" /> This article questions the extent to which *market power* and *gatekeeper powers* are substitute, or complements. While at first glance the DMA rests on a different analytical framework that enables to by-pass the exercise of market definition, this article shows that the DMA does not abandon key concepts attached to market power.

After recalling briefly what market and gatekeeper powers refer to (**section 1**), this article will discuss the analytical and procedural tools of market power assessment and gatekeeper designation (“the tools”) used under both regimes to establish the existence of market power and gatekeeper power. Then, we will compare market power and gatekeeper powers’ contribution to the *purposes* pursued by Article 102 TFEU and the DMA (“the purposes”).

Regarding the tools (**section 2**), analysis of market power in Article 102 TFEU involves a case-by-case definition of relevant market, calculation

<footnote n="6">⁶ For example, Germany amended competition law: in 2021 section 19a GWB (German Competition Act) was introduced to enable more effective, and earlier intervention against practices by large digital undertakings that are identified as having paramount significance for competition across markets. In the UK, the *Digital Markets, Competition and Consumers Act 2024* is a legislation that came into force creating the Digital Markets Competition Regime, applying to firms with having “strategic market status”.</footnote>

<footnote n="7">⁷ Regulation 2022/1925 on contestable and fair markets in the digital sector, OJ L265/2022 (the “DMA, 2022”).</footnote>

<footnote n="8">⁸ DMA, 2022, Recital 11.</footnote>

<footnote n="9">⁹ DMA, 2022, Recital 5; Judgment of the General Court of 17 July 2024, *ByteDance v. Commission*, T-1077/23, OJ C, C/2024/5325, paragraph 298.</footnote>

<footnote n="10">¹⁰ DMA, 2022, Recital 3 explains that gatekeepers are large undertakings with “considerable economic power”; Article 102 TFUE focuses on dominant undertakings, who are undertakings with “significant amount of market power”.</footnote>
of market shares, and assessment of power within that market.<fnref n="11" /> In digital contexts, the presence of gratuity, multi-sided, or ecosystem business models complexifies such tasks. While the European Commission (“the Commission”) and other authorities now take these into account,<fnref n="12" /> it has become increasingly difficult to rely on quantitative tools and metrics, such as the SSNIP<fnref n="13" /> test or market shares, to approximate market power. To remain accurate, the assessment must embrace more qualitative assessment. All this is case-specific and resource-intensive.<fnref n="14" /> In the DMA, the designation process of gatekeepers is (mostly) based on quantitative thresholds and purportedly moves away from market definition.<fnref n="15" /> This enables the use of clear quantitative metrics, which digital features barely allow in Article 102 TFEU. Yet, designation of gatekeepers under the DMA requires to delineate and qualify core platform services (“CPS”) with a qualitative assessment that may echo some discussions held in market definition.

Regarding the purposes (section 3), this article will compare the respective contribution of gatekeeper powers and market power to the legal instruments' objectives. The DMA's objectives, as expressly stated in the regulation title, are contestability<fnref n="16" /> and fairness.<fnref n="17" /> To put it simply, EU competition law, and as such Article 102 TFEU, may pursue variations of economic efficiency goals: the protection of the competitive process, or consumer welfare, within the Treaty-enshrined goal of EU market

<footnote n="11">¹¹ Guidance on the Commission’s enforcement priorities in applying Article 82 of the EC Treaty to abusive exclusionary conduct by dominant undertakings issued in December 2008 [2009] OJ C45/7 (“Guidance on Article 82”).</footnote>

<footnote n="12">¹² Commission Notice on the definition of the relevant market OJ C/2024/1645 [hereafter “Market definition Notice (2024)”].</footnote>

<footnote n="13">¹³ Small but significant non-transitory increase in price. Market definition notice (2024), paragraph 29 and footnote 53.</footnote>

<footnote n="14">¹⁴ A Fletcher, et al., “The effective use of economics in the EU Digital Markets Act”, *Journal of Competition Law & Economics* 20, no. 1-2 (2024): 1-19.</footnote>

<footnote n="15">¹⁵ Presumption based on quantitative thresholds set out in Article 3(2) of the DMA, 2022. “Any justification on economic grounds seeking to enter into market definition [...] should be discarded, as it is not relevant to the designation as a gatekeeper”. DMA, 2022, Recital 23.</footnote>

<footnote n="16">¹⁶ Defined in the DMA, 2022, Recital 32: “the ability of undertakings to effectively overcome barriers to entry and expansion and challenge the gatekeeper on the merits of their products and services”.</footnote>

<footnote n="17">¹⁷ Unfairness is defined in the DMA, 2022, Recital 33 as follows: “unfairness should relate to an imbalance between the rights and obligations of business users where the gatekeeper obtains a disproportionate advantage”.</footnote>
integration.<fnref n="18" /> While it may be the distinctive feature of the DMA, fairness seems to have been a revived principle in competition policy lately.<fnref n="19" /> This article argues that market and gatekeeper powers both contribute to contestability, albeit with variations: respectively with access to a user base for the DMA, and in a relevant market for Article 102 TFEU. Indeed, DMA designation decisions evidence that gatekeeper power is contestability-driven, with a distinctive dash of fairness. In sum, this article demonstrates that market power and gatekeeper power are substitutes in their respective use of quantitative and qualitative tools to approximate power, while being complements in the purposes they contribute to.

# 1. Market power and gatekeeper power: an introduction

## 1.1. Market power under Article 102 TFEU

Article 102 TFEU prohibits abusive conduct by undertakings in a dominant position. The concept of dominance, not defined in the Treaty but in the case law, amounts to a position of economic strength enjoyed by an undertaking enabling it to behave independently of competitors and consumers and, as such, giving the undertaking the ability to prevent competition.<fnref n="20" /> Being dominant in itself is not unlawful, but according to the doctrine of “special responsibility”, imposes the undertaking concerned to behave in such a way that does not impair “genuine”, undistorted competition.<fnref n="21" /> Economically, dominance refers to the holding of a substantial amount of market power, not in absolute terms, but with reference to a specific market. Under a basic economic definition, market power refers to the

<footnote n="18">¹⁸ For discussion of the goals of Article 102 TFEU see e.g. H. Schweitzer, S. de Ridder, “How to fix a failing Art. 102 TFEU: Substantive interpretation, evidentiary requirements, and the Commission’s future guidelines on exclusionary abuses”, *Journal of European Competition Law & Practice* 15, no. 4 (2024): 222-243; P. Akman, “Searching for the long-lost soul of Article 82 EC”, *Oxford Journal of Legal Studies* 29, no. 2 (2009): 267; I. Lianos, “Polycentric competition law”, *Current Legal Problems* 71 (2018): 161; K. Stylianou and M. Iacovides, “The goals of EU competition law: A comprehensive empirical investigation”, *Legal Studies* 42 (2022): 620; M. Iacovides, and K. Stylianou. “The new goals of EU competition law: Sustainability, labour rights, and privacy”, *European Law Open*, 2025: 1-30.</footnote>

<footnote n="19">¹⁹ See below section 3.</footnote>

<footnote n="20">²⁰ *United Brands Company and United Brands*, paragraph 65; Hoffmann-La Roche & Co. v. Commission, paragraph 38.</footnote>

<footnote n="21">²¹ Judgment of the Court of 9 November 1983, *Nederlandsche Banden-Industrie Michelin v. Commission*, C-322/81EU:C:1983:313, paragraph 57.</footnote>
ability to price over costs.<fnref n="22" /> Market power, under Article 102 TFEU, also refers to different parameters along which an undertaking can act independently of competitive constraints (output, innovation, quality...).<fnref n="23" /> The assessment of market power, a pre-requisite for the application of Article 102 TFEU, traditionally rests on a two-stage approach, involving first the definition of the relevant market in which the undertaking operates, the calculation of market shares within it, and assessment of specific market conditions or dynamics, such as barriers to entry or buyer power, that may contribute or mitigate the degree of market power.<fnref n="24" /> While these steps are followed in traditional markets, the assessment is less straightforward in digital contexts.

## 1.2. Gatekeeper power under the DMA

The DMA subjects “gatekeepers” to a set of obligations. Gatekeeper power is not defined as a concept, but with respect to qualitative features. Digital undertakings providing “core platform services” (CPS) may be designated as “gatekeepers”<fnref n="25" /> under three conditions: a) if they have a significant impact on the internal market, b) if they provide an important getaway for businesses to reach consumers, and c) if they enjoy an entrenched and durable position.<fnref n="26" /> The DMA contains an exhaustive list of ten “core platform services” whose provision may trigger the status of “gatekeepers”. The list includes intermediation services, search engines, social networks, video-sharing platforms, personal communication services, operating systems, and web-browsers.<fnref n="27" />

An undertaking providing a CPS will be presumed to meet the three conditions required to be a gatekeeper if it achieves turnover of (or more) than €7.5 billion in the last three financial years, or where its market value amounts to (or is above) €75 billion in the last financial year, and operating this CPS at least in three Member States, b) provides a CPS to at least 45 million monthly end users, and at least 10 000 yearly business users, all located in the EU, and c) meets each of the user thresholds (b) over the last

<footnote n="22">²² A. Hernandez Perez, A. Gonzalez, “Market power”, *Global Dictionary of Competition Law*, Con-currences.</footnote>

<footnote n="23">²³ Guidance on Article 82, paragraph 11.</footnote>

<footnote n="24">²⁴ Ibid., paragraphs 13-18.</footnote>

<footnote n="25">²⁵ DMA, 2022, Article 1.</footnote>

<footnote n="26">²⁶ Ibid., Article 3(1).</footnote>

<footnote n="27">²⁷ Ibid., Article 2(2).</footnote>
three years.<fnref n="28" /> To each of the qualitative criteria set out in Article 3(2) corresponds a quantitative threshold, the combination of which set a presumption of the existence of a “gatekeeper”. Such threshold-based approach enables clarity and speed in designation. Adjustment mechanisms, based on qualitative factors, exist to remedy the potential pitfalls of mechanic applications of quantitative thresholds.<fnref n="29" />

Any undertakings meeting the quantitative requirements in the provision of a CPS must notify the Commission, who will confirm (or not) the gatekeeper status within 45 working days.<fnref n="30" /> At the time of writing, seven undertakings have been designated as gatekeepers: Alphabet, Amazon, Apple, Booking, Byte Dance, Meta and Microsoft for a total of 24 core platform services.<fnref n="31" />

## 2. The tools for assessing market power and gatekeeper power

### 2.1. Market power assessment under Article 102 TFEU

Special market characteristics of digital markets complexify the evaluation of market power, as long built on tools fitted to traditional markets and centred on prices.<fnref n="32" /> **Section 2.1.1** discusses the challenges to market definition in digital contexts under Article 102 TFEU, which may explain why the DMA uses a drastically different methodological approach. Within the defined relevant markets, market power must be assessed based on market share calculation, which raises difficulties in digital contexts, and an analysis of relevant market conditions (**Section 2.1.2**).

#### 2.2.1. Market definition<fnref n="33" />

Market definition, within the hands of the competition authority, is aimed at establishing the boundaries of competitive constraints within which the

<footnote n="28">²⁸ Ibid., Article 3(2).</footnote>

<footnote n="29">²⁹ DMA, 2022, Article 3(5) and Article 3(8). See discussion in section 2.</footnote>

<footnote n="30">³⁰ DMA, 2022, Article 3(3) and 3(4).</footnote>

<footnote n="31">³¹ European Commission, “Gatekeepers”, available at https://digital-markets-act.ec.europa.eu/gatekeepers_en.</footnote>

<footnote n="32">³² See e.g. European Commission: Directorate-General for Competition, Y. Montjoye, H. Schweitzer, and J. Crémer, J., “Competition policy for the digital era”; *Publications Office* (2019), “Commission digital report”; OECD, “Rethinking antitrust tools for multi-sided platforms”, OECD Publishing, Paris (2018).</footnote>

<footnote n="33">³³ Although this article focuses on Article 102 cases, developments on market definition also consider merger cases as they also feature market definition, with common issues when it comes to digital markets.</footnote>
concerned undertaking's product or service operates. Defining the relevant market then enables the calculation of market shares, one key quantitative criterion used to assess the level of market power in Article 102 cases.<fnref n="34" />

Special features of digital platforms affect market definition in several ways: because of multi-sided and ecosystem characteristics, market definition firstly requires a “selection” step: should one, two, or platform/eco-system-based markets be defined (Section 2.1.1)? Once the markets are selected, gratuity and the dynamic features of digital markets particularly complicate the analysis of competitive constraints (Section 2.1.2).

The revised Commission notice on Market definition expressly acknowledges the most pressing challenges of digitisation.<fnref n="35" /> Although, to some, market definition has become irrelevant or inadequate in digital contexts,<fnref n="36" /> market definition's purposes may still be very important and normatively justified in how they provide contours to the Commission's action.<fnref n="37" /> This section thus explains how digital features demand more qualitative and data-intensive economic analysis. Not insurmountable, market definition under Article 102 TFEU is surely more costly and less certain.

### 2.1.1.1. Selecting markets

#### Multi-sided markets

A very common feature in digital markets is the existence of multi-sided platforms, acting as interfaces between distinct user groups, who produce indirect network effects on each other. In practice, it means that prices and consumer demand on one side of the platform exert constraints on the other side.<fnref n="38" /> This interdependence carries important implications in market definition, particularly regarding what markets to define or to select:

<footnote n="34">³⁴ Market definition notice, paragraphs 6-10.</footnote>

<footnote n="35">³⁵ Ibid., paragraphs 3, 14, 55, 94-104, 108; M. Eben, “The Draft Revised Market Definition Notice: The European Commission brings the relevant market further into the 21st century” *Kluwer Competition Law Blog* (2023), available at https://shorturl.at/YEiZb.</footnote>

<footnote n="36">³⁶ See e.g. L. Kaplow, “Why (ever) define markets”, *Harvard Law Review* 124, no. 2 (2010): 437; D. Glasner and S Sullivan, “The logic of market definition”, *Antitrust Law Journal* 83, no. 2 (2020): 293; C. Caffarra, “Joining competition policy with trade and industrial policy: Let’s Get Specific”, (2024) available at https://shorturl.at/SPWRc), and discussion in reports cited in n. 31.</footnote>

<footnote n="37">³⁷ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, Working Paper. CREATe (2024), available at https://lnkd.in/e9nuWYpp.</footnote>

<footnote n="38">³⁸ Seminal literature on two/multi-sided markets includes J.C. Rochet & J. Tirole, “Platform competition in two-sided markets”, *European Econ. Assn.* (2003): 1015; B. Caillaud & B. Jullien, “Competing cybermediaries”, *European Econ. Rev* 45 (2001): 797-808; “Chicken & egg: Competi-</footnote>
should one side, all of them, or the platform as a whole be defined? How to incorporate the crucial impact of interdependence on market definition?

Multi-sidedness has been particularly debated across jurisdictions, firstly in the context of card payment services.<fnref n="39" /> Over the past decade, as many cases opened in the digital economy, the way to select markets remained hesitant.<fnref n="40" /> In the merger control cases *Facebook/WhatsApp*<fnref n="41" /> and *Microsoft/LinkedIn*<fnref n="42" /> the different sides of the platforms were defined and considered (in distinction), while in *Google Search (Shopping)*<fnref n="43" /> only the search side was defined (with recognition of the importance of the advertising side). Although it demonstrates awareness, whether express or tacit, of multi-sidedness, no consensus emerged on what markets to select.<fnref n="44" /> In the EU, the revised market definition dedicates a section to market definition in the presence of multi-sided platforms. It explains that whether it is relevant to define the market as the platform as a whole, rather than on one specific side is determined by the substitution possibilities from one side to the other. The degree of interdependence between both sides should also be assessed.<fnref n="45" /> In *Apple – App Store Practices* (music streaming), the approach to multi-sidedness echoes the recent Market Definition Notice. There, the Commission finds that substitution patterns and competitive constraints

<footnote>tion among intermediation service providers”, *RAND J. Econ* 34 (2003): 309-328, D.S. Evans & R. Schmalensee, “Markets with two-sided platforms”, *Issues Competition L. & Policy* 1 (2008): 667.</footnote>

<footnote n="39">³⁹ In the US, multi-sidedness took a central place in the Supreme Court judgment. *Ohio et al. v. American Express Co.*, 585 U.S. (2018), 138 S. Ct. 2274, 2280, 2296 (2018). In the EU, see VISA and Mastercard cases where multi-sidedness was discussed and disputed. In the EU: Commission Decision of 9 August 2001, COMP/29.373, *Visa International* (2001), Commission Decision of 19 December 2007, COMP/34.579, *Mastercard* (2007).</footnote>

<footnote n="40">⁴⁰ M. Eben and V. H. S. E. Robertson, “Digital market definition in the European Union, United States, and Brazil: Past, present, and future”, *Journal of Competition Law & Economics*18, (2022): 417-455.</footnote>

<footnote n="41">⁴¹ Commission Decision of 29 August 2014, COMP/M.7217, *Facebook/WhatsApp* (2014), paragraphs 13-83.</footnote>

<footnote n="42">⁴² Commission Decision of 6 August 2016, COMP/M.8124, *Microsoft/LinkedIn* (2016), paragraph 388.</footnote>

<footnote n="43">⁴³ Commission Decision of 27 June 2017, AT.39740, *Google Search (Shopping)* (2017), paragraphs 145-250.</footnote>

<footnote n="44">⁴⁴ Although Eben and Robertson, “Digital market definition in the European Union, United States, and Brazil: Past, present, and future”, 447 saw the emergence of a coherent approach in the EU, in the distinction between transaction and non-transaction platforms, echoing the classification developed in L. Filistrucchi, D. Geradin, E. van Damme and P. Affeldt, “Market definition in two-sided markets: Theory and practice”, *Journal of Competition Law and Economics* 10, no. 293 (2014).</footnote>

<footnote n="45">⁴⁵ Market definition notice (2024) paragraphs 94-95.</footnote>
are very different between the end-users and developers, which imposes
two distinct markets to be defined, instead of a platform-wide definition.<fnref n="46" />

The Notice provides a welcome clarification for ongoing and future
cases. While awareness contributes to enhancing accuracy, market defi-
nition in such cases involves selecting the appropriate approach, which
seems to involve, at this stage already, some assessment of substitutability,
as exemplified in the *Apple – App Store Practices* (music streaming). In
addition, multi-sidedness is likely to imply multiple market definition, and
together with that, multiple burdensome analysis.

Digital ecosystems

Another feature of the digital economy is the development of ecosystems: an ecosystem is centred around a powerful orchestrator who connects multiple products, services and actors. These business models typically seek to induce consumers to use multiple related products or services. In effect, consumers may be locked into such ecosystems, and strategies that exploit the associated “bottlenecks” may be developed by those platforms.<fnref n="47" /> In addition, third party companies may be part of the system, even if they sometimes also offer competing products, as they bring more value to consumers as part of a competitor’s ecosystem.<fnref n="48" /> Businesses operating such eco-system do not just compete on specific products or services (e.g. provision of email or social network services), but on the overall integrated consumer experience that is specific to ecosystems. Market definition thus requires selecting which layers to consider: the product – level (the functionality), and/or ecosystem layers. The Commission’s digital report indicated that “firms compete to draw consumers into more or less comprehensive ecosystems, markets for specific products or services will persist from a consumer’s perspective, and should continue to be analysed separately, alongside competition on (possible) markets for digital ecosystems”.

Although increasingly mentioned and discussed,<fnref n="49" /> ecosystems were not
(expressly) analysed as such in market definition until the publication of

<footnote n="46">⁴⁶ Commission decision of 4 March 2024, AT.40437 – *Apple – App Store Practices (music stream-
ing)*, paragraph 272.</footnote>

<footnote n="47">⁴⁷ M. G. Jacobides, I. Lianos, “Ecosystems and competition law in theory and practice”, *Industrial and Corporate Change* 30, 5 (2021): 1199-1229.</footnote>

<footnote n="48">⁴⁸ F. Jenny, “Competition law and digital ecosystems: Learning to walk before we run”, *Industrial and Corporate Change* 30, no. 5 (2021): 1143-1167.</footnote>

<footnote n="49">⁴⁹ Judgment of the General Court of 14 September 2022, *Google and Alphabet v. Commission*, T-604/18, EU:T:2022:541, paragraph 116.</footnote>
the revised Market Definition Notice. In *Google/Fitbit*, or *Apple-App Stores Practices*, the Commission mentions ecosystems throughout the decisions, but not specifically in the context of market definition.<fnref n="50" /> In *Android*, Google tried to argue that they offered a “mobile platform system”, including an app store and an operating system, that would compete with Apple’s system, an approach the Commission rejected.<fnref n="51" /> Yet, multiple levels were discussed, and the distribution of component to the “smart mobile device” system indicate that the integrated level also has some relevance for the analysis.<fnref n="52" /> The revised market definition officially introduces ecosystems to the realm of market definition, recognising that ecosystems may be thought as comprising a primary core product, and secondary products, whose consumptions are connected, or offered, as a bundle.<fnref n="53" /> The Notice refers that it may be relevant to use after-market or bundle principles of market definition to define either a single “system” market, or two distinct (but related) markets.<fnref n="54" /> The selection of markets must be informed by factors such as the magnitude of network effects, consumer lock-in or multi-homing.<fnref n="55" /> Although a welcome addition, the Notice fails to provide clear guidance underlying selection of markets in digital ecosystems.<fnref n="56" /> According to Stylianou and Carballa-Smichowski, the aftermarket or bundle principles “only partially capture the breadth and complexity of ecosystems”, added to the fact that case law sets very specific conditions around those principles.<fnref n="57" /> They then propose a set of methods and tools – to be used sparingly, as being resource intensive – to help authorities determine whether it is relevant to depart from standard market definition to embrace an ecosystem definition.<fnref n="58" /> Going forward, at EU level, the revised

<footnote n="50">⁵⁰ Commission decision of 17 December 2020, M.9660, *Google/Fitbit*, C(2020)9105final(2020). Apple – App Store Practices (music streaming).</footnote>

<footnote n="51">⁵¹ Commission Decision of 18 July 2018, AT.40099, *Google Android* (2018) C(2018) 4761, paragraphs 296-299.</footnote>

<footnote n="52">⁵² Eben and Robertson, “Digital market definition in the European Union, United States, and Brazil: Past, present, and future”, 451.</footnote>

<footnote n="53">⁵³ Market definition notice (2024), paragraph 104.</footnote>

<footnote n="54">⁵⁴ Ibid., paragraphs 99-100.</footnote>

<footnote n="55">⁵⁵ Ibid., paragraph 104.</footnote>

<footnote n="56">⁵⁶ M. Eben, “The new market definition notice: Embracing change”, *Kluwer Competition Law Blog* (2024), available at https://shorturl.at/bCNnl.</footnote>

<footnote n="57">⁵⁷ K. Stylianou, B. Carballa-Smichowski, “Market’ definition in ecosystems”, *Journal of Antitrust Enforcement*, 2024, jnae046, https://doi.org/10.1093/jaenfo/jnae046, 2.</footnote>

<footnote n="58">⁵⁸ The methods involve data collection and analysis: hierarchical clustering, K-means clustering, network of complementarities, factor analysis, and snowball selection. Ibid., 30.</footnote>
Market definition may help make market definition more accurate, but the task seems increasingly burdensome.

### 2.1.1.2. Within selected markets: analysis of competitive constraints

Once the type and number of markets are selected in multi-market contexts, market definition involves an inquiry into sources of competitive constraints: demand substitution, supply substitution, and potential competition.<fnref n="59" /> Digital contexts are the cause of important hurdles to that end. Firstly, the main metric used to assess demand-side substitution, the SSNIP test, cannot be used in digital platforms using gratuity. Secondly, the fast-changing nature of such markets may require a more dynamic interpretation of substitution (both on the demand and the supply side), which gives greater importance to potential competition. This means that an analysis of competitive constraints needs to be more forward-looking and, as any prospective analysis, is difficult and uncertain.

## Inadequacy of the SSNIP test

First of all, it has been long recognised that markets do exist even when products or services are free. Gratuity does not preclude the existence of an economic activity, since there are alternative parameters to price competition, such as quality.<fnref n="60" /> That being said, the use of the SSNIP test, a metric used to infer the availability of a substitute product from the profitability (or not) of a small but sustained price rise over a given product, seems particularly ill-suited to zero-priced services. Indeed, the difficult evaluation of whether users of, for example, search engines have substitutes to switch to when there is no monetary price for its use has driven authorities and courts to depart from the SSNIP test in the presence of non-paying users. In addition, the SSNIP test is particularly complex to operate in the case of multi-sided platforms, connecting one paying party (e.g. advertisers) and another accessing the service for free (e.g. users of a social network). The interdependence among the two sides means a small increase in price has an impact on demand and prices on the other side, which in turn affects prices and demand on the other side. This “chicken-and-egg” problem is characteristic of network effects (be they direct or indirect), another salient feature of digital markets that complicates the use of price-centric

<footnote n="59">⁵⁹ Market definition notice (2024), paragraph 23.</footnote>

<footnote n="60">⁶⁰ Eben and Robertson, “Digital market definition in the European Union, United States, and Brazil: Past, present, and future”, 430-433.</footnote>
tools. The revised Market Definition Notice acknowledges the difficult use
of the SSNIP test in digital markets, incorporating alternatives, such as the
“SNDQ” test (theoretical decrease in quantity), suggested by the General
Court in Android.<fnref n="61" /> Alternative concepts to prices that ought to be used to
assess substitutability include innovation, sustainability, value and variety
of uses, privacy.<fnref n="62" /> Added to the pre-existing criteria used to assess sub-
stitutability (such as product functionality or intended use), the revised
definition notice contributes to enhance accuracy of market definition in
presence of gratuity. Yet, the wide range of possible criteria decreases pre-
dictability of market definition outcomes.

Fast-changing markets

In fast-changing and innovation-intensive markets, the evolution of com-
petitive constraints is more dynamic that in traditional markets. This
affects, and complicates, both the supply and demand sides of substitution,
as well as potential competition.

Regarding potential competition, in the assessment of the *Tomtom/*
*TeleAtlas* merger, in 2008, the Commission stated that Google's entry in
the navigable digital map market was unlikely, or not timely, in the EEA.<fnref n="63" />
Already active in the US, Google maps entered the EEA market shortly
after the Commission decision. While this analysis was part of the com-
petitive assessment, this reflects the potential difficulty of assessing the
likelihood of potential competition in dynamic markets. In the *Google
Search (shopping)* decision, the Commission discussed the extent to which
online retailers and merchant platforms (such as Amazon) set competitive
constraints on Google on the shopping comparison functionality. Based
on a careful consideration of market data, the conclusion was that mer-
chant platforms only acted as limited substitutes for users and sellers. One
of the arguments advanced by the Commission, and supported by the GC
in the appeal, is that Google Shopping did not sell products directly to
users but acted as an intermediary between sellers and shoppers. While
they offered similar multi-brand comparison experience to users, mer-
chant platforms (such as Amazon) provided the possibility for direct
purchase and orders to be processed, which makes them very distinctive

<footnote n="61">⁶¹ Judgment of the General Court of 14 September 2022, *Google and Alphabet v. Commission* (Google Android), T- 604/18 ECLI:EU:T:2022:541, paragraphs 176-177. Commission Digital report 45.</footnote>

<footnote n="62">⁶² Market definition notice (2024), paragraph 30.</footnote>

<footnote n="63">⁶³ Commission decision of 14 May 2008, COMP/M.4854 – TOMTOM/TELEATLAS, paragraph 158.</footnote>
both for users and retailers.<fnref n="64" /> A more dynamic enquiry may have entailed prospection of whether Google Shopping was likely to develop into a merchant place. Indeed, in 2018, Google Shopping started to feature direct purchase functionalities in some countries as part of the *Google Shopping Actions* or *Buy on Google* programmes, which were discontinued in 2023.<fnref n="65" /> In addition, a delivery service, *Google express*, was introduced in the US in 2019, to close the same year. Had such features been further expanded and sustained, Google Shopping would have possibly warranted a different market definition.<fnref n="66" />

Regarding the demand side, the analysis of substitution may also be more uncertain due to changes in how digital products are consumed. In 2014, when assessing the *Facebook/WhatsApp* merger, while the Commission considered that there was some overlap between the functions offered by the two companies, notably with Messenger, it concluded that “Facebook and WhatsApp are not close competitors”.<fnref n="67" /> The assessment focused on the distinctive user experience provided by Messenger, given its integration to Facebook’s social network. This analysis was surely appropriate, based on the analytical framework followed by the Commission, and at the time. Yet, this overlooked the fact that WhatsApp was becoming a close competitor to Facebook: given the stellar user growth witnessed by WhatsApp in the 2010s, many Facebook users had probably been migrating their social interactions to the benefit of WhatsApp. Indeed, the latter also offered, through group chats, collective sharing of messages and multimedia content, on top of the single-messaging facility. Considering how much Facebook valued this transaction in 2014, Facebook was surely anticipating that WhatsApp was becoming “the new Facebook”: a very close competitor, not just to Messenger but to Facebook’s social network in general.<fnref n="68" />

<footnote n="64">⁶⁴ *Google Search (Shopping)* (2017), paragraphs 207-250, General Court, *Google and Alphabet v. Commission*, paragraphs 482-483.</footnote>

<footnote n="65">⁶⁵ Google, “Help shoppers take action, wherever and however they choose to shop”, available at https://blog.google/products/ads/shopping-actions/Shopify, “Buy on Google”, https://shorturl.at/7QTfc.</footnote>

<footnote n="66">⁶⁶ Tech Crunch, “Google Express to close in a few weeks, will become part of Google Shopping”, available at https://shorturl.at/9YGCw, Global Data, “Google Forays into Ecommerce – Competition among E-retailers Intensifies”, available at https://shorturl.at/NRutj.</footnote>

<footnote n="67">⁶⁷ *Facebook/WhatsApp*, paragraph 107.</footnote>

<footnote n="68">⁶⁸ One view, corroborating the “killer acquisition” scenario is that “Facebook acquired the rights to oversee and monetize the transition from one of its products to another”. NY Mag, “How Meta is monetizing the decline of Facebook” (2023), https://nymag.com/intelligencer/2023/11/how-meta-</footnote>
The revised Market Definition Notice embraces the challenges of dynamic competition. It explains the need to adopt a forward-looking approach when structural changes in competitive constraints are “sufficiently foreseeable”.<fnref n="69" /> Indeed, the Commission may adopt a forward-looking approach to market definition when there is evidence that changes in general dynamics of supply and demand (structural changes) are expected to take place with a sufficient likelihood. It is clarified that these considerations differ from a potential competition analysis, which is more strictly focused on likelihood of entry by individual actors.<fnref n="70" /> The Market Definition Notice therefore embraces the critical importance of dynamic competition stemming both from change in supply and change in demand, yet this forward-looking assessment may be either uncertain or resource-intensive.

To sum up, digital features complexify market definition in two main ways: often multi-product markets (when multi-sided platforms or digital ecosystems) demand selection of what markets to define prior to undertaking the actual definition of the relevant market. Second, the analysis of competitive constraints moves away from quantitative metrics, given the gratuity of services and the fast-changing nature of such markets. Such account in the revised Notice increases accuracy and awareness, yet potentially placing greater weight on forward-looking assessment, which in essence is more uncertain. As such, market definition may not be insurmountable, but the necessary methodological adjustments make its outcome less predictable.

### 2.1.2. Market shares and relevant “market conditions”

Once a relevant market is identified, competition authorities must assess market power within such markets to establish dominance. Dominance is usually established based on a two-stage approach, involving the calculation of market shares in the relevant market and consideration of “relevant market conditions” and “dynamics of the market”.<fnref n="71" /> Undertakings with market shares above 50% in the relevant market are typically presumed to

<footnote>is-monetizing-the-decline-of-facebook-with-whatsapp.html. On the topic of killer acquisitions in competition law see e.g. C. Cunningham, F. Ederer and S. Ma, “Killer acquisitions”, *Journal of Political Economy* 129, no. 3 (2021): 649. OECD, “Start-ups, killer acquisitions and merger control – Background note”, DAF/COMP(2020)5.</footnote>

<footnote n="69">⁶⁹ Market definition notice (2024), paragraph 8.</footnote>

<footnote n="70">⁷⁰ Ibid., paragraph 21.</footnote>

<footnote n="71">⁷¹ Guidance on Article 82, paragraphs 13-18.</footnote>
be dominant, while it is very unlikely for undertakings with market shares below 40% to be found dominant.<fnref n="72" /> An assessment of economic market conditions, including barriers to entry, may be particularly important to rebut the finding of dominance in the case of large market shares, or to the contrary, to establish it, for levels below 50%.<fnref n="73" />

In the digital economy, the assessment of market power may be more complex. Market shares may be a less accurate proxy for dominance in the context of digital markets.<fnref n="74" /> Firstly, due the disruptive power of innovative concepts and tools, large market shares at a given time may not necessarily reflect dominance, as they can be short-lived. This phenomenon is (too?) often exemplified by the drastic decline of *MySpace* in 2009, when it was surpassed by Facebook, after being the largest social network in the world from 2005 to 2009.<fnref n="75" /> For different reasons, but equally disruptively, Zoom became leader in the videoconferencing market at the outbreak of the Covid crisis in 2020.<fnref n="76" /> The decisional practice has long recognised that “in fast-growing markets with short innovation cycles, high market shares in themselves may be a less useful indicator of market power given that those shares may turn out to be ephemeral”.<fnref n="77" /> Nevertheless, large market shares may still indicate dominance if stable over time. In *Google Shopping*, for example, the Commission considered, among other factors used to establish dominance, that a market share of above 90% of online search was held for 8 years.<fnref n="78" />

Secondly, in multi-sided markets, a one-sided market share may fail to provide a complete picture of market power, while a platform-wide market

<footnote n="72">⁷² Hoffmann-La Roche & Co AG v. Commission, Judgment of the Court of 3 July 1991, AKZO Chemie BV v. Commission, C-62/86, ECR 1991 I-03359, paragraph 60. See discussion in B. Sufrin, N. Dunne and A. Jones, *Jones & Sufrin's EU competition law* (8th edition, Oxford University Press, 2023), 363.</footnote>

<footnote n="73">⁷³ B. Sufrin, N. Dunne and A. Jones, *Jones & Sufrin's EU competition law*, 366 and Judgment of the Court of First Instance of 17 December 2003, *British Airways v. Commission* T-219/99, EU:T:2003, 343.</footnote>

<footnote n="74">⁷⁴ *Jones & Sufrin's EU competition law*, 369.</footnote>

<footnote n="75">⁷⁵ Financial Times. “The rise and fall of MySpace”, 2009. Available at https://shorturl.at/32rj7.</footnote>

<footnote n="76">⁷⁶ Demandsage, “Zoom user statistics 2025 – Market share & revenue” (2024) available at https://www.demandsage.com/zoom-statistics/.</footnote>

<footnote n="77">⁷⁷ Judgment of the general Court 11 December 2013, *Cisco Systems and Messagenet v. Commission*, T-79/12, EU:T:2013:635, paragraph 69 and the European Commission, “draft Guidelines on exclusionary abuses under Article 102 TFEU”, paragraph 28 (“draft Guidelines on exclusionary abuses”).</footnote>

<footnote n="78">⁷⁸ *Google Search (Shopping)*, paragraph 274.</footnote>
share may not capture all competitive dynamics and constraints affecting only one side.<fnref n="79" /> Finally, gratuity should not preclude the calculation of market shares, as alternative metrics to value of sales can be found (e.g. user number instead of value of sales).<fnref n="80" />

The reduced importance of market shares means that “relevant market conditions” are likely to be assessed more thoroughly, with greater depth of economic analysis.<fnref n="81" /> Expansion or entry, closely linked to how contestable markets are, deserve particular attention in digital markets. Contributors to market power, particularly featuring in digital markets, include the existence of network effects, multi-sided platforms, and ecosystems. The ability of consumers to switch to other products, to multi-home, or suppliers to enter production are also key factors. In digital contexts, the importance of consumer behaviour and the inertia, a tendency to stick to services offered by default, has also received traction in the decisional practice and among competition authorities.<fnref n="82" /> Analysis of such factors is also more qualitative in nature and requires resource intensive economic analysis, including behavioural economics.<fnref n="83" /> As such, the assessment of market power, from market definition to economic factors, is more qualitative and more data-intensive in digital contexts. For the sake of conciseness and given the extant literature on such market power contributors in digital markets, no further discussion will be provided here.

## 2.2. Designation of gatekeepers under the DMA

The DMA was introduced to address entrenched economic power in digital markets. The DMA was also deliberately designed to ensure clarity, speed, and administrability in its enforcement, which Article 102 TFEU seems unable to achieve in digital contexts.<fnref n="84" /> The impact assessment who informed the DMA proposal thus logically considered various methodology

<footnote n="79">⁷⁹ OECD (2022), “The evolving concept of market power in the digital economy”, paragraph 13.</footnote>

<footnote n="80">⁸⁰ Commission digital report, 48-49. See also J. Franck, and M. Peitz, “Market definition and market power in the platform economy”, (2019), report, Centre on Regulation in Europe (CERRE), 71-73.</footnote>

<footnote n="81">⁸¹ Guidance paper on Article 82, paragraphs 13-18.</footnote>

<footnote n="82">⁸² See in general *Jones & Sufrin's EU competition law*, 381; OECD (2022), “The evolving concept of market power in the digital economy”.</footnote>

<footnote n="83">⁸³ A. Fletcher, “The role of behavioural economics in competition policy”, in *Cambridge handbook on the theoretical foundations of antitrust and competition law*, ed. Justin Lindenboom (Cambridge University Press, forthcoming 2025).</footnote>

<footnote n="84">⁸⁴ A. Fletcher, et al., “The effective use of economics in the EU Digital Markets Act”.</footnote>
options to remedy the issues of a burdensome and lengthy task of mar-
ket definition in digital contexts.<fnref n="85" /> The DMA indeed distances itself from
market definition tools. “Any justification on economic grounds seeking to
enter into market definition [...] should be discarded, as it is not relevant to
the designation as a gatekeeper”.<fnref n="86" /> In *ByteDance*, the Commission unsur-
prisingly refused to consider arguments advanced by ByteDance referring
to market definition precedents in competition law cases.<fnref n="87" /> On top of the
procedural aspects, one substantive argument may justify avoiding formal
market definition.<fnref n="88" /> The distinctive objectives of the DMA, those of ensur-
ing contestability and fairness, especially the latter, do not justify identi-
fication of harm on a given market, as clarified in the DMA and recalled
by the General Court in *ByteDance*.<fnref n="89" /> I will return to the objectives of the
DMA in the following section.

The designation of gatekeeper under the DMA, as described in section 1,
involves two methodological steps: first, the identification of whether they
provide a CPS (section 2.2.1), second, if they act as a gatekeeper for such
CPS (section 2.2.2), fulfilling the criteria of having a significant impact
on the internal market, providing a gateway service, and holding an
entrenched position. While the second step largely rests on quantitative-
based presumptions, the identification of a CPS may resemble, in some
ways, the discussion held in the context of market definition.<fnref n="90" />

2.2.1. *Identification of CPS providers*

Although the DMA set an established list of services that amount to
CPS with complete definitions for each of them<fnref n="91" />, there are still conten-
tious issues that potential gatekeepers might use in an attempt to contest

<footnote n="85">⁸⁵ European Commission: Directorate-General for Communications Networks, Content and Technology, Sunderland, Jet al., *Digital Markets Act – Impact assessment support study – Annexes*, Publications Office, 2020, https://data.europa.eu/doi/10.2759/230813, 100-101.</footnote>

<footnote n="86">⁸⁶ DMA, 2022, Recital 23.</footnote>

<footnote n="87">⁸⁷ Commission Decision of 5 September 2023, DMA.100040 *ByteDance – online social networking services*, paragraph 65.</footnote>

<footnote n="88">⁸⁸ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, 25.</footnote>

<footnote n="89">⁸⁹ DMA, 2022, Recital 11; General Court, *ByteDance v. Commission*, paragraph 19.</footnote>

<footnote n="90">⁹⁰ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, 26.</footnote>

<footnote n="91">⁹¹ DMA, 2022, Articles (2)(4)-(14).</footnote>
their designation in the *delineation* and *qualification* of CPS.<fnref n="92" /> To recall, the DMA identified ten CPS that include online intermediation, social networks, online search, operating systems, and online advertising.<fnref n="93" />

## Delineation

The delineation of the boundaries of a CPS is required when an undertaking provides several services, sometimes in an integrated manner or offered as part of ecosystems. A question is whether the interconnected services offered by the same undertakings form part of the same CPS. This is an important point, since the delineation of CPS is likely to have an impact on both the meeting of quantitative thresholds and on the scope of the DMA's obligations, which are different based on the type of CPS identified.<fnref n="94" /> The DMA, in its Annex, clarifies that when an undertaking provides two services that do not belong to the same category of CPS, as defined under the DMA, they should be considered to be distinct CPS, even if provided in an integrated way.<fnref n="95" /> In *Alphabet*, the Commission logically recalls that services that are integrated into Google Search (e.g. Google shopping results prompted by a general search) must be considered as distinct “intermediation” CPS from the CPS “search engine”.<fnref n="96" /> However, if such two services do not correspond to different CPS, the Commission will consider the purposes of usage of the service by end users and business users: if purposes are different, the integrated services will be outside the scope of the CPS.<fnref n="97" /> This is where a case-by-case discussion of purposes and uses may recall in some ways discussions of purpose and intended used in market definition. Indeed, in *Booking.com*, following a detailed discussion of

<footnote n="92">⁹² F. Bostoen and G. Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act” *TILEC Discussion Paper No. 2024-16*, 4. A; Ribera Martínez, “The requisite legal standard of the Digital Markets Act’s designation process”, *Journal of Competition Law & Economics* 20, 4 (2024): 265-291.</footnote>

<footnote n="93">⁹³ DMA article 2(2).</footnote>

<footnote n="94">⁹⁴ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, 27.</footnote>

<footnote n="95">⁹⁵ DMA, 2022, Annex D, c, i.</footnote>

<footnote n="96">⁹⁶ Commission decision of 5 September 2023, DMA.100011, 100002, 100004-100006, 100009, 100008 and 100010 *Alphabet* – OIS verticals, OIS app stores, online search engines, video sharing, number-independent interpersonal communications services, operating systems, web browsers, online advertising services, paragraph 96.</footnote>

<footnote n="97">⁹⁷ DMA, 2022, Annex D, c ii. “In such cases, a relevant criterion for identifying distinct CPSs within the same category of CPSs is the purpose for which the service is used by either end users or business users, or both”. See booking.com, paragraph 12.</footnote>
services features and usages by both user groups of each of the connected services, the Commission considered that Agoda, KAYAK, OpenTable and Priceline, as well as BNSA advertising service, were not part of the online intermediation CPS.<fnref n="98" /> In contrast, Rentalcars.com was considered to be within the same intermediation CPS, as the hotel and car rental services are used as a conduit to the same travel services offering provided through Booking.com.<fnref n="99" /> It is interesting to note that the delineation takes a major part in the Commission’s decision (14 out of 25 pages). This despite both parties having agreed on most of the CPS delineation questions.<fnref n="100" />

Another important delineation issue is whether different CPS must be identified when the same service is provided through different devices (e.g. mobile phone, desktop, tablet). In its designation decisions, the Commission most of the times decided that a service would constitute a single CPS irrespective of the device through which it is offered, consistently with the technology neutral approach set in the DMA.<fnref n="101" /> Nonetheless, the Commission departed from device neutrality in relation to the operating system CPS provided by Apple. Under the DMA, the definition of the operating system relates closely to the hardware and, hence, the technology, which allows device-specific considerations.<fnref n="102" /> Exceptionally, thus, the Commission considered Apple’s OS to be a distinct CPS depending on the devices used (e.g. IOS for mobile phones, for tablets etc.). An analysis of purposes and usages (reflected in the data on use time, number of downloads, and application activations) showed distinct App usages by end-users, depending on the device. In addition, app developers specifically develop apps for a given type of device.<fnref n="103" /> In contrast, but more in line

<footnote n="98">⁹⁸ Commission Decision of 13 May 2024, DMA.100019, *Booking – Online intermediation services, verticals*, paragraphs 38-72.</footnote>

<footnote n="99">⁹⁹ Ibid., paragraph 54.</footnote>

<footnote n="100">¹⁰⁰ Both parties disagreed in the finding that BSNA, advertising service, is outside of the online intermediation CPS. In any case, this did not imply the identification of a second CPS due to BSNA not fulfilling the gatekeepers criteria. Ibid., paragraph 72.</footnote>

<footnote n="101">¹⁰¹ “For the purposes of this Regulation, the definition of core platform services should be technology neutral and should be understood to encompass those provided on or through various means or devices”, Recital 14 and Bostoen and Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act”, 5.</footnote>

<footnote n="102">¹⁰² Commission Decision of 5 September 2023, DMA.100013, 100025, 100027, *Apple – online intermediation services* (app stores), operating systems and web browsers, paragraph 83.</footnote>

<footnote n="103">¹⁰³ Ibid., paragraphs 90-91.</footnote>
with the technology neutrality of the DMA, Alphabet's operating system was delineated as one single CPS.<fnref n="104" />

## Qualification of CPS

Another set of issues relates to the “classification” or “qualification” of CPS. No longer about the boundaries of the CPS, the qualification questions within which type of CPS a given service falls. ByteDance’s service TikTok falls into the definition of two CPS – both a video-sharing platform<fnref n="105" /> and social network.<fnref n="106" /> While ByteDance notified its gatekeeper status as a video-sharing CPS provider, the Commission took the view that it was instead a social network. This was subject to disagreement. ByteDance argued that TikTok’s primary purpose was to provide users with short-video content, even though it also offered features of social networks.<fnref n="107" /> To the contrary, the Commission considered that video-sharing was one feature of the social network, and that the classification of social network “best reflects the characteristics and breadth of TikTok’s features and functionalities”.<fnref n="108" /> Interestingly, the Commission refuted ByteDance’s argument according to which classification must centre on the “essential functionality” of TikTok as video-sharing platform. It explained, in contrast, that the CPS definition of social networking demanded to adopt a more encompassing approach, which included integrated social networking features.<fnref n="109" /> Finally, the Commission refuted any argument borrowed from market definition precedents as irrelevant to the designation process.<fnref n="110" /> Qualification was also required to assess whether Instagram and Facebook were part of a single or two distinct social network CPS offered by Meta. While Meta argued that both were forming part of a single social network CPS, the Commission considered distinct technical features, on

<footnote n="104">¹⁰⁴ DMA.100011 et seq., Alphabet, paragraph 164.</footnote>

<footnote n="105">¹⁰⁵ DMA, 2022. Article 2(8) referring to Audiovisual Media Services Directive, Recital 4: “Video-sharing platform services provide audiovisual content which is increasingly accessed by the general public, in particular by young people. This is also true with regard to social media services, which have become an important medium to share information and to entertain and educate, including by providing access to programmes and user-generated videos”.</footnote>

<footnote n="106">¹⁰⁶ DMA, 2022, Article 2(7): “online social networking service means a platform that enables end users to connect and communicate with each other, share content and discover other users and content across multiple devices and, in particular, via chats, posts, videos and recommendations”.</footnote>

<footnote n="107">¹⁰⁷ DMA.100040, *ByteDance*, paragraphs 28-35.</footnote>

<footnote n="108">¹⁰⁸ Ibid., paragraph 42.</footnote>

<footnote n="109">¹⁰⁹ Ibid., paragraph 48.</footnote>

<footnote n="110">¹¹⁰ Ibid., paragraph 65.</footnote>
the one hand (the distinct branding, platforms and apps, distinct accounts, registration processes), and on the other hand their different social functionalities and purposes in terms of content shared, and who the users are (e.g. typically, older on Facebook than on Instagram).<fnref n="111" />

## Identification of CPS providers and market definition

The Commission recalled in *Alphabet* that the delineation of a CPS “has no bearing on the definition of the relevant market for the purpose of applying EU competition rules (and vice versa) and those two types of analyses may thus lead to different results”.<fnref n="112" /> Yet, as explained, the analysis involved in the identification of CPS providers may share commonalities with market definition. Similarly to CPS delineation, market definition asserts the outer boundaries of products or services among themselves. The inclusion or exclusion of connected services in the delineation of CPS recalls the market selection process detailed in section 2.1.1.1. Features and functionalities at the heart of discussions on CPS resemble discussions on the product characteristics, functionalities, intended use, and general customer preferences in market definition.<fnref n="113" /> Yet, no discussion of sources of competitive constraints (substitutability, potential competition) is present in the CPS identification.<fnref n="114" /> Some authors have identified inconsistencies in the process of CPS identification and thus demand more predictability.<fnref n="115" /> Inherently linked to the nascent nature of the DMA, the difficulties may also be akin to those present in market definition, who attempts to respect precedents, while recalling that the assessment is case-specific. In addition, despite the definition efforts of CPS in the DMA, the presence of multi-product firms (integrated and ecosystems) necessarily blurs boundaries. Yet, given it is a shared task between undertakings and the

<footnote n="111">¹¹¹ Commission decision of 5 September 2023, DMA.100020, 100024, 100035 and 100044, *Meta – online social networking services, number-independent interpersonal communications services, online advertising services, OIS marketplace*, paragraphs 44-57.</footnote>

<footnote n="112">¹¹² DMA.100011 et seq., *Alphabet* paragraph 19.</footnote>

<footnote n="113">¹¹³ Market definition notice (2024) paragraphs 48-50.</footnote>

<footnote n="114">¹¹⁴ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, 27.</footnote>

<footnote n="115">¹¹⁵ A. Ribera Martínez, “The requisite legal standard of the Digital Markets Act’s designation process”, highlighting particular inconsistencies in how “purposes” are considered in the delineation of CPS; Bostoen and Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act” identify several “steps” into how delineation is made: definition found in DMA and other regulations, principle of device neutrality, consideration of CPS purposes for business and end-users, 7.</footnote>
Commission, the identification of CPS seems less burdensome than what market definition of similar platforms entails under Article 102 TFEU.<fnref n="116" />

### 2.2.2. Gatekeeper designation

Once an undertaking is identified as providing a CPS, it is designated as a gatekeeper if it has a significant impact on the internal market, provides a gateway service, and holds an entrenched position. Such criteria are presumed to be fulfilled upon meeting quantitative thresholds exposed in section 1. The DMA provides detailed definition of those metrics to remove all possible ambiguity in the self-assessment of thresholds by undertakings.<fnref n="117" /> The clarity and simplicity of quantitative threshold-based presumptions contrasts drastically with the assessment of market power in digital contexts. But these thresholds only yield a presumption of the existence of a gatekeeper power, which may be rebutted. The DMA provides adjustment mechanisms to remedy situations when gatekeeper power does not exist despite being within thresholds (Article 3(5): rebuttals),<fnref n="118" /> or when gatekeeper status exists outside of the thresholds (Article 3(8) Qualitative designations).<fnref n="119" /> This section discusses the extent to which these adjustments reintroduce the analysis of barriers to entry akin to that used in the assessment of market power.

## Article 3(5): rebuttals

Undertakings can rebut the gatekeeper presumption if they provide evidence to demonstrate that “exceptionally”, in spite of meeting the quantitative thresholds, they are not gatekeepers within the meaning of qualitative criteria laid down in Article 3(1).<fnref n="120" /> Rebuttals were accepted immediately in the case of Samsung’s browser<fnref n="121" /> and email services offered by Microsoft (Outlook)<fnref n="122" /> and Alphabet (Gmail)<fnref n="123" />, and accepted following

<footnote n="116">¹¹⁶ M. Eben, “A renewed vision of market definition’s importance: Competition law in the collective interest”, 27.</footnote>

<footnote n="117">¹¹⁷ DMA, 2022, Annex E.</footnote>

<footnote n="118">¹¹⁸ Ibid., Article 3(8).</footnote>

<footnote n="119">¹¹⁹ Ibid., Article 3(5).</footnote>

<footnote n="120">¹²⁰ Ibid.</footnote>

<footnote n="121">¹²¹ Commission Decision of 5 September 2023, DMA.100038, *Samsung – web browsers*.</footnote>

<footnote n="122">¹²² Commission Decision of 5 September 2023, DMA.100017, DMA.100023, DMA.100026, *Microsoft – online social networking services, number-independent interpersonal communications services and operating systems*, paragraphs 125-137.</footnote>

<footnote n="123">¹²³ DMA.100011 et seq., *Alphabet*, paragraphs 139-151.</footnote>
a market investigation in relation to Apple's iMessage,<fnref n="124" /> TikTok Ads,<fnref n="125" /> and Microsoft's online search Bing, web browser's Edge, and advertising Ads.<fnref n="126" />

Pursuant to recital 23 of the DMA, evidence adduced as part of rebuttals must “directly relate to quantitative criteria” such as (emphasis added): the size, in absolute terms, and the number of Member States receiving the service, user numbers compared to the threshold, scale of activities of the CPS, and number of years.<fnref n="127" /> The recital goes on referring that “any justification on economic grounds seeking to enter into market definition or to demonstrate efficiency [...]” should be discarded. One important question is, since it particularly lists metrics-based elements, whether recital 23 enables qualitative arguments to be provided by undertakings. In ByteDance, the General Court confirms that the types of evidence found in recital 23 are not exhaustive, and that qualitative arguments have a place to the extent they relate to the requirements set out in Article 3(2). As such, not only “figures” may be provided to rebut a presumption, but qualitative evidence as well. The only excluded types of evidence are those relating to market definition and economic efficiencies.<fnref n="128" /> Is such qualitative evidence related to quantitative criteria the only admitted evidence? Or are admitted qualitative and quantitative relating to other criteria,? The Commission answers this.<fnref n="129" /> In Alphabet and Microsoft, the Commission states that “while multi-homing, network effects or lock-in effects regarding users’ ability to switch may be relevant to assess the existence of a gateway position, the existence of multi-homing, the lack of network effects, or lock-in effects are not, in themselves, necessarily an indication that a CPS does not constitute an important gateway for business users to reach end users”.<fnref n="130" /> In addition, the Commission states in Meta that “the presence of insurmountable barriers to entry and expansion” is not required for

<footnote n="124">¹²⁴ Commission decision of 13 May 2024, DMA.100042, *ByteDance – online advertising services*.</footnote>

<footnote n="125">¹²⁵ Commission decision of 12 February 2024, DMA.100015, *Microsoft Online search engines*; DMA.100028 *Microsoft Web browsers*; DMA.100034, *Microsoft Online advertising services*.</footnote>

<footnote n="126">¹²⁶ Commission decision of 12 February 2024, DMA.100022 Apple – *number independent interpersonal communications service*.</footnote>

<footnote n="127">¹²⁷ DMA, 2022, Recital 23.</footnote>

<footnote n="128">¹²⁸ DMA.100040, *ByteDance – online social networking services*, paragraphs 36-55.</footnote>

<footnote n="129">¹²⁹ See also A. Ribera Martínez, “The requisite legal standard of the Digital Markets Act’s designation process”, 20, identifying specifically the type of qualitative arguments considered in each decision.</footnote>

<footnote n="130">¹³⁰ DMA.100011 et seq., *Alphabet*, paragraph142, DMA.100017 *Microsoft – online social networking services*, paragraph 126.</footnote>
finding that a CPS constitutes an important gateway.<fnref n="131" /> The DMA indeed recognises that there may be more than one gatekeeper operating in the same CPS category.<fnref n="132" /> This means that although evidence (qualitative or quantitative) about barriers to entry may be admitted, their assessment will typically carry less weight than in market power assessment, as barriers to entry and a plurality of gatekeepers can co-exist. This may be at odds with the objective of contestability, which is developed in the following section. Logically, in *ByteDance*, the Commission thus did not discard in principle arguments related to the network effects, multi-homing and lock-in advantages derived from ecosystems, which were also subject to detailed discussion in the General Court's judgment.<fnref n="133" />

**Article 3(8) Qualitative designations**

In the same vein, the Commission also has the possibility to designate gatekeepers if it considers that gatekeepers meet the qualitative, despite not meeting the quantitative criteria.<fnref n="134" /> Article 3(8) details the factors that the Commission will consider. These comprise the quantitative factors used in Article 3(5), such as size, turnover and market value, and numbers of users. Qualitative factors are also part of the assessment. These include network effects, data-driven advantages, scale and scope effects, switching costs, as well as behavioural biases (e.g. inertia) reducing multi-homing possibilities, as well as business models offering an integrated provision of related services. The assessment must also be forward-looking and include an assessment of structural evolutions, including acquisitions.<fnref n="135" /> Interestingly, the draft Guidelines on exclusionary abuses under Article 102 TFEU mirror the quantitative factors listed in the DMA: the enriched paragraph on barriers to entry specifically mentions “data-driven advantages”, switching-costs, including “behavioural biases”, as well as vertical integration strategies.<fnref n="136" /> Additionally, the new paragraph on platform markets discusses how network effects can create barriers to entry and concludes that “entry barriers resulting from network effects may be even

<footnote n="131">¹³¹ DMA.100020 et seq., *Meta – online social networking services*, paragraph 297.</footnote>

<footnote n="132">¹³² DMA, 2022, Recital 32: “Contestability of the services in the digital sector can also be limited if there is more than one gatekeeper for a core platform service”.</footnote>

<footnote n="133">¹³³ DMA.100040, *ByteDance – online social networking services*, paragraph 127; General Court, *ByteDance v. Commission*, paragraphs 163-215.</footnote>

<footnote n="134">¹³⁴ DMA, 2022, Article 3(8).</footnote>

<footnote n="135">¹³⁵ Ibid.</footnote>

<footnote n="136">¹³⁶ Draft Guidelines on exclusionary abuses, paragraph 30.</footnote>
higher when users single-home". This means that as in the DMA, multi-homing may not preclude or mitigate market/gatekeeper power, but single-homing definitely aggravates it.<fnref n="137" />

Following a market investigation, Apple's iPadOS was designated as gatekeeper despite falling below the quantitative criteria. The Commission considered quantitative factors, namely the number of end users being falling just shortly below the threshold, the leading "shares" of IPads (and thus, iPadOS) from all tablets sold in the EU, as well as business users being 10 000 above the thresholds.<fnref n="138" /> In the assessment of qualitative factors contributing to the provision of a gateway service, the Commission considered how end-users and business users are locked-in, together with the benefits of network and scale effects on the OS.<fnref n="139" />

As such, there is no complete symmetry between methodology and evidence used by parties when presumptions do not hold: the Commission has greater tools and arguments at disposal, including those akin to market power assessment, showing perhaps that qualitative Article 3(8) designations may be less “exceptional” in nature than successful rebuttals and warranting different evidentiary burdens.<fnref n="140" />

## 2.3. Tools: substitutes or complements?

Previous developments on the tools show how digital contexts may challenge the assessment of market power, which the DMA has been designed to remedy. Indeed, under Article 102, taking into consideration special features may enhance accuracy of market power assessment, but reduces the possible reliance on quantitative tools, such as the SSNIP test and market shares. As a result, qualitative assessments of market conditions such as barriers to entry carries more weight in the overall assessment of market power. This comes with greater cost and uncertainty. The DMA thus voluntarily overcomes such hurdles in adopting quantitative thresholds-based presumptions. As such, gatekeeper designation introduces quantitative metrics that is now missing in the assessment of market power. Gatekeeper and market power appear as substitutes regarding the use of quantitative analysis. Yet, this needs to be nuanced. Gatekeeper

<footnote n="137">¹³⁷ Ibid., paragraph 31.</footnote>

<footnote n="138">¹³⁸ Commission Decision of 29 April 2024, DMA.100047, *Apple – iPadOS*, paragraphs 28-36.</footnote>

<footnote n="139">¹³⁹ Ibid., qualitative factors are also quantitatively substantiated, paragraphs 37-114.</footnote>

<footnote n="140">¹⁴⁰ Arguments well developed by A. Ribera Martínez, “The requisite legal standard of the Digital Markets Act’s designation process”.</footnote>
designation, in its two stages (identification of a CPS and whether a gate-
keeper provides it) is not exempt from qualitative analysis, which may echo
that used in market power assessment. Although CPS are well-defined in
the DMA, their identification, especially in multi-product firms, involves
discussions of boundaries, of “features and functionalities” akin to discus-
sion of purposes, and intended uses held in market definition. Still, CPS
identification is not about interchangeability and competitive constraints,
which remains the exclusivity of market definition. Regarding the notion
of gatekeeper, reliance on threshold-based presumptions reinjects a great
dose of quantitative methods. Nonetheless, the thresholds only set pre-
sumptions given that gatekeepers are still primarily defined qualitatively.
As such, qualitative assessment and analysis of barriers to entry, akin to
that in market power, still play a role when thresholds may not apply. As
explained, parties are not equal in how they can use such arguments: while
barriers to entry arguments remain exceptional, with less weight when
used in rebuttals by undertakings, they may form substantial parts of the
Commission’s assessment in its qualitative designations under Article
3(8). In sum, DMA’s designation may be a very useful substitute method to
market definition in digital contexts: more quantitative and more predict-
able, yet with a complementary scope and outcomes.

3. *Gatekeeper and market power's contribution to the purposes of Article 102 TFEU and the DMA*

This section turns to compare the respective contribution of gatekeeper
power and market power to the objectives pursued by Article 102 TFEU
and the DMA. It shows that both concepts contribute to contestability,
albeit with a twist. Under Article 102 TFEU, dominant undertakings are
firms with “significant amount of market power”, enabling them to behave
“independently of competitors and consumers”.<fnref n="141" /> Under the DMA’s terms,
gatekeepers are undertakings with “considerable economic power”, “bar-
gaining power”, and their status is defined with reference to an “entrenched
and durable position”, with “significant impact on the internal market”.<fnref n="142" />
Both gatekeeper and market powers feature undertakings with strong eco-
nomic power. Yet, the DMA carefully avoids referring to market power of
gatekeepers. It also explains how it remedies the shortcomings of Article

<footnote n="141">141 *United Brands*, paragraph 65; *Hoffmann-La Roche & Co. v. Commission*, paragraph 38.</footnote>

<footnote n="142">¹⁴² DMA, 2022. Recitals 3 and 4, Article 3.</footnote>
102 TFEU, which is “limited to certain instances of market power, for example dominance on specific markets”, adding that gatekeepers (under the DMA) are “not necessarily dominant in competition-law terms”.<fnref n="143" /> In *ByteDance*, the General Court indeed recalled that gatekeepers “do not necessarily hold a dominant position within the meaning of competition law”.<fnref n="144" /> Nonetheless, this section will demonstrate that both market and gatekeeper powers may contribute to the purpose of contestability, respectively with access to a user base and in a relevant market. **Section 3.1** firstly determines that both Article 102 TFEU and the DMA largely overlap on contributing to ensuring contestability in digital markets. **Section 3.2** explains how, under EU law, the concept of gatekeeper closely relates to lack of contestability. **Section 3.3** particularly analyses designation decisions under the DMA, to compare gatekeeper power and market power’s contribution to contestability.

### 3.1. *Purposes of the DMA and Article 102 TFEU*

To put it simply, EU competition law may pursue variations of economic efficiency goals: the protection of competitive process, or consumer welfare, within the Treaty-enshrined goal of EU market integration.<fnref n="145" /> Over the past decades, although the enforcement of competition law may have centred on economic efficiency, wider goals, including fairness, may now be pursued at least politically.<fnref n="146" /> According to its very own title, the DMA has as objectives to ensure “contestability” and “fairness” in digital markets, supposedly “complementary to, but different” from the competition law goals of “protecting undistorted competition”.<fnref n="147" /> Contestability is defined in the DMA as “the ability of undertakings to effectively overcome barriers to entry and expansion and challenge the gatekeepers on the merits of their products and services”.<fnref n="148" /> This clearly corroborates the economic-efficiency objective of Article 102 TFEU, prohibiting conduct by dominant

<footnote n="143">¹⁴³ Ibid., Recital 5.</footnote>

<footnote n="144">¹⁴⁴ General Court, *ByteDance v. Commission*, paragraph 298.</footnote>

<footnote n="145">¹⁴⁵ See references in note 17.</footnote>

<footnote n="146">¹⁴⁶ Commission Communication “A competition policy fit for new challenges”, COM(2021)713, 1: “By basing our policy intent and action on principles that stem directly from the Treaties, EU competition policy is able to pursue multiple goals, such as fairness and level-playing field, market integration, preserving competitive processes, consumer welfare, efficiency and innovation, and ultimately plurality and democracy”.</footnote>

<footnote n="147">¹⁴⁷ DMA, 2022, Recital 11.</footnote>

<footnote n="148">¹⁴⁸ Ibid., Recital 32.</footnote>
firms that departs from “competition on the merits”.<fnref n="149" /> The DMA defines fairness negatively: “Unfairness should relate to an imbalance between the rights and obligations of business users where the gatekeeper obtains a disproportionate advantage”.<fnref n="150" /> Article 102 TFEU also prohibits “unfair practices”, and as such fairness protects against market power abuse, especially now that fairness seems revived.<fnref n="151" /> The DMA’s definition of fairness seems to include distributional considerations and actively promote equal competitive conditions, which sounds more expansive than what Article 102 TFEU entails.<fnref n="152" /> Yet, while at first glance “fairness” may be the outlier, the DMA and Article 102 TFEU are both part of the overall EU digital competition policy that expands its intervention beyond the consumer welfare standard.<fnref n="153" /> As such, their purposes seem to be largely substitutes, albeit with a twist.

## 3.2. Gatekeeper power and contestability under EU law

This section explains that the very concept of “gatekeeper”, which existed before the DMA, is inherently related to the issue of lack of contestability. The concept of gatekeeper, not new in EU economic law, including in EU competition law, may generically be defined as intermediaries who are able to “control access by a group of users to some goods or another group of consumers”.<fnref n="154" /> Under such definition, gatekeeper power may be akin to a competitive bottleneck in network industries in which the intermediary controls a limited resource or capacity and which gives power to the intermediary as the only way to access a resource. For example, the *European Electronic Communications Code* regulates such power derived from control over bottleneck facility and imposes obligations of access to safeguard

<footnote n="149">¹⁴⁹ P. Ibáñez Colomo, “Competition on the merits”, *Common Market Law Review* 61, 2 (2024): 387-416.</footnote>

<footnote n="150">¹⁵⁰ DMA, 2022, Recital 33.</footnote>

<footnote n="151">¹⁵¹ For the evolving role, and concept of fairness in competition law, see e.g. N. Dunne, “Fairness and the challenge of making markets work better”, *Modern Law Review* 84 (2021): 230; G. Colangelo, “In fairness we (should not) trust: The duplicity of the EU competition policy mantra in digital markets”, *Antitrust Bulletin* 68, 4 (2023): 618.</footnote>

<footnote n="152">¹⁵² E. Garces, and G. Colangelo, “Markets, competition, and fairness”, in *Research handbook on competition and corporate law*, eds. F. Thépot and A. Tzanaki (Edward Elgar Publishing, forthcoming 2025), 19.</footnote>

<footnote n="153">¹⁵³ Ibid., 8.</footnote>

<footnote n="154">¹⁵⁴ P. Alexiadis, and A. de Stree!, “Designing an EU Intervention Standard for digital platforms”, *EUI Working Paper* RSCAS 2020/14 (2020), 5, available at https://shorturl.at/ckSzB.</footnote>
competition.155 In competition law, the existence of gatekeeper power, enabled by the control over access to technical services, already featured in merger control in several pay TV mergers.156 In *NewsCorp/Telepiu*, the Commission expressly discussed how the merging entity would be a “gatekeeper” of a technical tool and platform on which competitors would critically depend to offer their own channels to users.157 Here, the term gatekeeper signified considerable amount of market power, to the point that a merger would be prohibited if the gatekeeper position was not remedied by a compulsory access provision.158 Gatekeeper power under the DMA may imply high degree of power over user groups, which must be regulated to ensure contestability. Indeed, in the DMA, gatekeepers may be seen as holding considerable power in the provision of a CPS in relation to users and businesses, who may not have no option but to remain with the gatekeepers. The magnitude of power would justify imposing quite intrusive *ex ante* obligations outside of the existence of competitive harm. This would echo the ample policy concerns that digital markets have “tipped” in favour of a few digital platforms to a point that no *ex-post* enforcement, including remedies, would solve contestability issues identified.159 Is the contestability-driven conception of gatekeeper power supported in the DMA’s decisional practice? If so, to what extent does that echo market power’s contribution to contestability under Article 102 TFEU?

### 3.3. Gatekeeper power and contestability under the DMA

This section examines how, in the DMA, the concept of gatekeeper contributes to contestability, and how this compares with market power's contribution under Article 102 TFEU. While contestability may seem relative in gatekeeper designation compared to market power assessment (section 3.3.1), gatekeeper distinctively contributes to contestability, not in a relevant market, but in respect to user groups (Section 3.3.2). This is the “fairness” twist of the DMA.

<footnote n="155">155 Directive 2018/1972 of the European Parliament and of the Council of 11 December 2018 establishing the European Electronic Communications Code, OJ [2018] L 321/36, Recital 28.</footnote>

<footnote n="156">156 A. de Streel, “Gatekeeper power in the digital economy: An emerging concept in EU law”, OECD, DAF/COMP/WD(2022)57. Some of the mergers were also cleared upon compulsory access granted to such technical services.</footnote>

<footnote n="157">157 Decision of the Commission of 2 April 2003, M.2876 *NewsCorp/Telepiu*, paragraph 198.</footnote>

<footnote n="158">158 Ibid., paragraph 225.</footnote>

<footnote n="159">159 DMA, 2022. Recitals 25 and 26 indeed refers to the market tipping in favour of large digital undertakings.</footnote>
### 3.3.1. *The relative importance of contestability under the DMA*

In gatekeeper designation, the absence of market power, and quantitative evidence thereof, such as minor usage of a service, compared to others, may be very important to the Commission when assessing the rebuttal of quantitative designations.<fnref n="160" /> Yet, contestability required for intervention under the DMA may be for lower levels of power than its dominance equivalent. In *ByteDance*, the General Court indeed confirmed that gatekeepers may not have an “assailable” position and, as such, the concept “does not preclude the existence of a certain degree of contestability”.<fnref n="161" /> While this resembles the statement that dominance “does not preclude some competition”,<fnref n="162" /> this twist to contestability may also remind that it is only a co-objective to fairness in the DMA. This relative contestability also appears as follows.

Firstly, several gatekeepers can operate within the same CPS, while under Article 102 TFEU there is usually no more than one dominant undertaking for a given market.<fnref n="163" /> Recital 32 indeed says that “contestability of the services in the digital sector can also be limited if there is more than one gatekeeper for a core platform service”.<fnref n="164" /> To illustrate this, five gatekeepers were designated as intermediation providers, three of them as social network providers.<fnref n="165" /> Secondly, the relative importance of contestability under the DMA also manifests itself in relation to the question of challengers to gatekeepers. ByteDance contested its designation as gatekeeper for TikTok on the grounds that it was not a gatekeeper, but a challenger to other gatekeepers, notably Meta and Alphabet. One question is whether a contestability-driven designation would preclude a challenger being a gatekeeper at the same time. While the Commission clearly stated the possible co-existence of a challenger and its gatekeeper,<fnref n="166" /> the General Court took a view more aligned with that of contestability: it argued that while TikTok was a challenger in 2018, it is now a gatekeeper,

<footnote n="160">¹⁶⁰ Bostoen and Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act”, 22.</footnote>

<footnote n="161">¹⁶¹ General Court, *ByteDance v. Commission*, paragraph 300.</footnote>

<footnote n="162">¹⁶² *Hoffmann-La Roche & Co. AG v. Commission*, paragraph 39.</footnote>

<footnote n="163">¹⁶³ Leaving the specific conditions of collective dominance aside.</footnote>

<footnote n="164">¹⁶⁴ Recital 32.</footnote>

<footnote n="165">¹⁶⁵ European Commission, “Gatekeepers”, available at https://digital-markets-act.ec.europa.eu/gatekeepers_en.</footnote>

<footnote n="166">¹⁶⁶ DMA.100040 *ByteDance – online social networking services*, paragraph 159.</footnote>
a position which was rapidly consolidated.<fnref n="167" /> Some have argued that the Commission’s position on challengers, not rejected by the General Court, is at odds with the overall objective of contestability pursued by the DMA. Indeed, challengers may be the best positioned to safeguard contestability of users of such platforms. Subjecting them to the DMA may be costly and burdensome for such challengers.<fnref n="168" /> Similarly, although digital ecosystems may reinforce the position of gatekeepers, with respect to other CPS providers, the General Court confirmed that lacking an ecosystem does not prevent a CPS from constituting a gateway service.<fnref n="169" /> In *ByteDance*, the general Court clarifies that a case-by-case assessment must show how benefits derived from the ecosystem affect the contestability of the CPS.<fnref n="170" /> However, gatekeeper power exists, not in relation to a service or any relevant market equivalent, but in relation to businesses and end users.

### 3.3.2. Contestability in relation to user groups

Refocusing the issue of contestability on users and businesses, the ability of both user groups to switch to other platforms should be critical to the non-designation of gatekeepers. If both business users and end-users are able to use several competing platforms, no platform may have significant power over those. Yet, in *ByteDance*, the General Court clarified that although being a relevant factor, the possibility of multi-homing is no proof that there is no gatekeeper power. Especially so in social networks, where it is very frequent for users to use various platforms. As such, given that multi-homing possibilities may be asymmetric between end users and businesses, a precise account of such dependence must be provided for each user group.<fnref n="171" /> The General Court added that dependence on a service is determined by how “important” it is to such users.<fnref n="172" />

<footnote n="167">¹⁶⁷ General Court, *ByteDance v. Commission*, paragraph 315.</footnote>

<footnote n="168">¹⁶⁸ J. van den Boom, “Incumbent or challenger? Assessing ecosystem competition in the DMA”, *Journal of Competition Law & Economics* 20, 4 (2024): 409-444, Bostoen and Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act”, 27-28.</footnote>

<footnote n="169">¹⁶⁹ A digital ecosystem is defined by the General Court as consisting of “one or more CPSs and other services connected to them, for example by means of technological links or interoperability; this is liable to exacerbate entry barriers for competitors of those undertakings and increase the cost of switching providers for end users, making it more difficult for existing or new market operators to compete with those undertakings or contest their position”. General Court, *ByteDance v. Commission*, paragraph 128.</footnote>

<footnote n="170">¹⁷⁰ Ibid., paragraph 134.</footnote>

<footnote n="171">¹⁷¹ Ibid., 163-215.</footnote>

<footnote n="172">¹⁷² Ibid., 210.</footnote>
As such, dependence on specific business users to a platform seems more
critical than how contestable a user base is in absolute terms. This twist to
contestability may remind us that the DMA also pursues fairness: users
must be protected from being disadvantaged due to their dependence on a
platform, even if there are alternative providers and a sufficient degree of
contestability. Gatekeeper power may thus induce *economic dependence*,
which echoes the doctrine traditionally rooted in contract or commercial
law in various jurisdictions, referring to abuses of imbalance of power
in business-to-users or business-to-business relationships.<fnref n="173" /> In its pro-
posal for the Platform-to-Business Regulation, the Commission actually
referred to platforms being “quasi-gatekeepers” to markets and consum-
ers, leading to an increased dependence of businesses.<fnref n="174" /> Coming back to
the DMA, gatekeeper power also induces imbalances in bargaining power,
a source of unfair practices towards businesses and users. As such, des-
ignation logically takes place outside of contestability, and even outside
of the competition law conception of fairness.<fnref n="175" /> Yet, as the designation
practice shows, criteria used to approximate the notion of “gateway” (scale
of usages as opposed to other designated gatekeepers in that category or
on the presence of an ecosystem) largely echoes the contestability analysis
with which market power coincides.<fnref n="176" />

Conclusion

This article compared the concept of market power under Article 102 TFEU with that of gatekeepers under the DMA. While the assessment of market power moves away from quantitative methods, for greater accuracy, the DMA reinjects a great dose of quantitative-based tools. Although in a varied intensity, both analyses of market power and gatekeepers comprise an assessment of qualitative factors, revolving around barriers to entry. In addition, issues of boundaries' delineation feature in both methodologies. The tools on which they rely are substitutes, but with complementary scope and outcomes. Market power and gatekeepers also largely overlap in how they contribute to the goals pursued by Article 102 TFEU

<footnote n="173">¹⁷³ A. de Streel, “Gatekeeper power in the digital economy: An emerging concept in EU law”, 4; OECD (2022), “The evolving concept of market power in the digital economy”, 28.</footnote>

<footnote n="174">¹⁷⁴ Explanatory Memorandum of the Commission Proposal for a Regulation on promoting fairness and transparency for business users of online intermediation services, COM(2018) 238</footnote>

<footnote n="175">¹⁷⁵ E. Garces and G. Colangelo, “Markets, competition, and fairness”, 19.</footnote>

<footnote n="176">¹⁷⁶ Bostoen and Monti, “The rhyme and reason of gatekeeper designation under the Digital Markets Act”.</footnote>
and the DMA. They may be substitutes regarding how contestability drives their application, while complements, in the way the concept of gatekeepers expands the reach of intervention against unfair conduct towards end users and businesses. Finally, gatekeeper power appears as a variation of market power, in its scope, and with a distinctive dash of fairness.

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