MarsEdit started as a blog posting feature in NetNewsWire by Brent Simmons. It was then expanded and moved into a standalone app. Daniel Jalkut of Red Sweater Software acquired the app in 2007 and he is still the current developer. Daniel blogs about MarsEdit at: https://red-sweater.com/blog/
MarsEdit can download posts, create new posts, edit and delete posts, and upload files. It works with most popular blogging software including Blogger, Movable Type, Tumblr, WordPress, and Micro.blog. It supports 3 very different APIs:
- MetaWeblog XML-RPC API (with flavors for the original Blogger API, Movable Type API, and the WordPress API)
- AtomPub API (used for Google's Blogger)
- Tumblr API (custom JSON-based API)
MarsEdit will auto-discover the API type and endpoint using Really Simple Discovery (RSD): https://en.wikipedia.org/wiki/Really_Simple_Discovery
MarsEdit does not currently support the Micropub API. At IndieWebCamp Austin 2017, one of the sessions discussed improvements to Micropub specifically with an app like MarsEdit in mind.