Interoperability between the products and services of different firms promotes competition by lowering switching costs. Requiring dominant firms to make their products interoperable, or reducing barriers to interoperability, are important components of competition policy for the digital age. [...] It explains the problem of “gatekeeper” firms in Internet-related markets, and describes the ways that Internet services can interoperate with one another, including through “competitive compatibility” achieved without permission from an incumbent firm. Interoperability frequently happens without significant coordination between an incumbent firm and a challenger. Many entrepreneurs build new products or services to be compatible with existing ones by reverse-engineering the existing product and deriving the technical requirements for interoperability, often without permission from the incumbent. Many important innovations have come from such “competitive compatibility.” For example, Cydia was a long‑running alternative app store for Apple devices that featured software programs that were not available from Apple or Apple‑authorized developers. (2022) source Unverified