The significance of API-first development is that it allows tech companies to prioritize the creation of Application Programming Interfaces in their projects. This approach ensures that every feature is accessible via an API, enabling greater flexibility and scalability. By focusing on APIs first, developers can create more modular applications, fostering easier integration with third-party services. This agility not only expedites the development process but also enhances user experience by allowing faster implementation of new features. As businesses increasingly rely on data sharing and interoperability, API-first development becomes crucial for future growth and innovation.