Adversarial interoperability is Cory Doctorow's term for the practice of making a product or service work with a competitor's product without the competitor's permission or cooperation — and against the competitor's active attempts to prevent it. The "adversarial" qualifier distinguishes the practice from cooperative interoperability (where companies agree on shared standards) and from mere compatibility (where products happen to work together).
The concept became central to Doctorow's framework for how digital markets became concentrated and how that concentration might be reversed.
Definition and Scope
Adversarial interoperability covers a wide range of practices:
Doctorow's key insight is that adversarial interoperability was historically a normal feature of competitive technology markets — and that its suppression is a relatively recent development enabled by intellectual property law and technical lock-in mechanisms.
Historical Examples
Doctorow grounds the concept in concrete history. Early Microsoft Word grew by reading WordPerfect files. Lotus 1-2-3 was displaced partly because competitors reverse-engineered its keyboard commands. Early internet services competed by building on top of each other without permission. VisiCalc lost to Lotus because Lotus could read VisiCalc files; Lotus lost to Excel partly because Excel could read Lotus files.
In each case, an incumbent's market dominance was disrupted not by building a better product in isolation but by connecting to the incumbent's user base — taking their data and social connections with them to the competitor. This dynamic, Doctorow argues, is what made technology markets competitive.
Why It Matters Now
Doctorow's argument, developed extensively on pluralistic-blog and in the-internet-con, is that today's platform monopolies — Google, Amazon, Apple, Meta — have successfully suppressed adversarial interoperability through a combination of:
The result is that the historical mechanism by which market entrants could challenge incumbents has been legally blocked. switching-costs have risen dramatically. Users who want to leave Facebook cannot take their social graph with them; users who want to leave Amazon cannot take their purchase history. This, Doctorow argues, is not a natural feature of digital markets but a legal and political achievement by incumbents.
Relationship to Other Concepts
Adversarial interoperability is Doctorow's preferred term for the practice; competitive-compatibility is the term he sometimes uses interchangeably, with slightly different emphasis (see that entry). The distinction is partly rhetorical: "adversarial" foregrounds the political and legal conflict, "competitive compatibility" foregrounds the market outcome.
interoperability-mandates represent the policy prescription: if voluntary adversarial interoperability is being suppressed, government mandates could require platforms to expose interfaces. Doctorow treats adversarial interoperability and interoperability mandates as complementary tools.
The concept connects to end-to-end-principle thinking: a network architecture that keeps the network neutral and pushes intelligence to the edges naturally enables adversarial interoperability; an architecture that centralizes control blocks it.
enshittification is partly the story of what happens in the absence of adversarial interoperability — lock-in enables the extraction sequence.
Adoption
The term was taken up by electronic-frontier-foundation in policy advocacy and has been used in regulatory discussions in the EU (Digital Markets Act) and US contexts. lina-khan's FTC explored interoperability requirements in platform markets, and Doctorow's framing influenced how advocates described the problem. tim-wu and zephyr-teachout have engaged with similar arguments about interoperability as a competition tool.