Micropub

Micropub is an open API standard that is used to create posts on one's own domain using third-party clients.

w3.org/TR/micropub
W3C Recommendation
micropub.rocks
Test suite and debugging utility
Implementation Reports
The Micropub specification is developed under the W3C Social Web Working Group.
The specification was contributed to the W3C by the IndieWeb community. More information and history of the spec can be found on the IndieWeb wiki.