What file uses .md extension and how should I edit them?

Question

On GitHub, several projects have README.md files. It seems like a simple format file to express text and pictures.

I guess there is an editor or syntax

Answer 1

I suggest StackEdit. It is simple WISIWIG editor. You can use both editor and markdown syntax. There is a quick markdown help syntax there. Undo/redo, comments, GoogleDrive, Dropbox interconnection.