Does Digital Platform Interoperability Deliver on Its Expectations? Evidence from User Switching on Mastodon

Users of centralised digital platforms (e.g., X, Instagram, TikTok) have little choice but to accept incumbent providers’ conduct or forgo participation. Digital platform interoperability is widely proposed as a remedy to reduce the economic and political power of centralised digital platforms by enabling user choice without sacrificing network connectivity. Despite its prominence in policy debates (e.g., EU’s Digital Markets Act, Art. 7), theoretical claims on its effects remain largely untested. This paper evaluates three theoretical expectations on platform interoperability: that it neutralises proprietary network effects; it facilitates individual user choice and switching; and that technical standardisation risks homogeneous services. To operationalise these concepts, this study analyses user switches within the interoperable social platform Mastodon. It draws on an unobtrusive, qualitative analysis of user posts documenting why individuals switched their interoperable providers. My findings qualify the theoretical promises and concerns: I find that interoperability is necessary but, on its own, insufficient to achieve the intentions associated with policy proposals. I identify practical obstacles such as incomplete implementation, information costs, and persistent switching costs that preserve proprietary network effects and that hinder individual choice and switching. Further, I challenge the concern of anticipated service homogenisation. I identify avenues of vertical (e.g., quality) and horizontal (e.g., governance values) provider differentiation. These avenues form an emerging research agenda on new dynamics between differentiated but interoperable platform providers. Overall, this study contributes the first empirical evaluation of digital platform interoperability, identifies obstacles, and formulates recommendations, speaking directly to policy.