The 8th International Workshop on Web APIs and Service Architecture (WS-REST 2017) is the 2017 edition of the WS-REST Workshop Series. Hosted by the renowned WWW conference series at the 2017 event in Perth, Australia, WS-REST 2017 brings together a community of researcher and practitioners interested in Web APIs and service architecture. APIs have become the connective fabric of the Web and any application area that uses Internet or Web technologies. The goal of WS-REST 2017 is to provide a forum for researchers and practitioners where they can openly and freely exchange ideas about how they are using Web technologies in their APIs, what works and what does not work for them, and what challenges they see in the current landscape of standards and technologies. Our goal is to capture both the state of the art when it comes to Web APIs and service architecture, but to also provide a forum that identifies some of the most pressing issues in that space, and can help solving them.