API is technology and digital product used for artificial intelligence, platform economy, and internet. It has the capability to change business models dramatically. APIs (application programming interfaces) are becoming a major competitive factor for companies. This book takes on the fundamental questions of API Economy and approaches the subject pragmatically and clearly without technical jargon. The book clarifies the birth and shape of the API Economy with numerous practical examples. This is the first API Economy book based on scientific references. Originally this popular book was written in Finnish. It is a great start for students and advanced professionals alike. After reading this book, you will understand what it is all about and how to move forward and grow your business with APIs. The authors are leading Finnish API-experts with an abundance of experience from API and platform economy as authors, researchers, and lecturers and consultants.