The significance of APIs in software integration lies in their ability to facilitate communication between diverse software applications. By defining the protocols for how different systems interact, APIs allow developers to create more cohesive ecosystems, enabling functionalities such as data sharing, third-party service integration, and automation. This ease of interoperability promotes innovation and efficiency, as developers can leverage existing services rather than building everything from scratch. APIs ultimately enhance the user experience by enabling seamless interactions across various platforms and technologies.