Gatekeeper: DMA's big-platform rule

Under the Digital Markets Act, a gatekeeper is a company that runs a core platform service—like a search engine, app store, or social network—and holds a powerful position as the middleman between businesses and end users. The key test is whether the platform has a large user base, a strong economic position, and an entrenched role that makes it hard for others to compete. Unlike a GDPR data controller, who decides how personal data is processed, a gatekeeper is defined by its market power and the bottleneck it creates, not by its data-handling role.

To spot a gatekeeper question, remember the three thresholds: at least 45 million monthly active end users in the EU, at least 10,000 yearly business users, and a market capitalisation over €75 billion or equivalent revenue. If a question lists these numbers, it is pointing to DMA gatekeeper designation, not GDPR. A useful trick is to think of the gatekeeper as the "toll booth" that businesses must pass through to reach customers—this image helps separate it from other roles like data processor or controller.

For a quick self-test, ask: does the platform control access between two distinct groups (businesses and consumers) and meet the size criteria? If yes, it is a gatekeeper. If the question instead focuses on who decides the purpose of data processing, it is a data controller under GDPR. Keep the toll-booth image in mind to avoid mixing up the two concepts.