Web Application Open Platform Interface (WOPI) is a protocol that enables a client to access and change files stored on a server. The protocol was first released as version 0.1 by Microsoft in January 2012, [1] and as of August 2025 the specification is at version 15.1. The protocol has been adopted by applications outside of Microsoft, such as by Collabora Online, Google, ownCloud and Nextcloud. [2] [3] [4] [5]