The paper tries to figure out the possible competitive outcomes in the field of metaverse, taking stocks of previous experiences in the digital economy. Competition among Virtual Worlds could either take the form of a market where each Virtual World constitutes a separate relevant market (due to lock-in effects), or results in a market that tips, so where a monopolist prevails. To avoid such outcomes, interoperability is key. In this regard, the article offers some examples to demonstrate the importance of interoperability rules to ensure competition, considering interoperability standards adopted by other industries (such as the financial one). In conclusion, the paper foresees the “inevitability” of interoperability in the metaverse due to the possible application of the Digital Markets Act to Virtual Worlds.