Haroopad is described as 'markdown enabled document processor for creating web-friendly documents. You can author various formats of documents such as blog article, slide, presentation, report, and e-mail as if experts did' and is a popular Text Editor in the News & Books category. There are more than 100 alternatives to Haroopad for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and iPhone. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Vim or Zettlr. Other great apps like Haroopad are Atom (Free Personal, Open Source), Sublime Text (Free Personal), Typora (Paid) and Mark Text (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Zettlr is a supercharged markdown editor that combines many writing editor features and collect them in one application. It aims at speeding up your workflow and help you write without any interruptions.
GNU Emacs is an extensible, customizable text editor—and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing. The features of GNU Emacs include: