From the World Wide Web Consortium (W3C):
Micropub is a client-to-server protocol used to create, update and delete social networking content. Web and native apps can use Micropub to post notes, photos, events, and many others to servers that support the protocol. Users can choose to create content in a variety of client posting interfaces, while maintaining control of where the data is stored.
Prior to being adopted by the W3C Social Web Working Group for standardization, Micropub already had over a dozen independent implementations in the IndieWeb community. There are now over a dozen independent client and server implementations across a wide variety of languages and platforms.
Direct to Micropub Recommendation (May 23, 2017)