There are many free open-source markdown editors for Windows. I’m certain of this, because the SourceForge directory lists 35 projects that qualify as an “open source” Markdown editor. You can filter these by OS, license, language, project status, etc.
I’ll be focusing on three: MarkText (the one that seems to be most prominently documented), VNote and Ghostwriter. For example, Marker stores everything in your own filesystem. There’s nothing to install, you can use any web browser and it works great.
MarkText
What is MarkText? MarkText is a fast, user-friendly, cross-platform markdown editor written in C++/Qt and released under MIT licensing. It focuses on speed and usability.
You need Windows 10 or later with at least 2 GB of RAM and a modern processor to run MarkText. MarkText is actively developed with regular updates, and community sponsors it. The latest version is always free from its GitHub release page. MarkText supports math expressions via KaTeX, front matter, emojis, and so on.
The MarkText installer file is named marktext-win-(x64|arm64)-%version%-setup.exe.
VNote
VNote is a markdown note-taking application based upon Qt and native C++. According to its website, it “focuses on Markdown.” It also supports markdown, rich text, plain text, and other formats.
Ghostwriter
Ghostwriter is identified as a free and open-source markdown editor recommended as an alternative.
WYSIWYG?
Some markdown applications are known as WYSIWYG — What You See Is What You Get. In essence, markdown is plain-text, which means that unless you render it using an application that renders markdown, it will appear as unrendered text. A few open-source markdown applications render your markdown right there, such as vrite.io. StackEdit is another one; however, I think the latter may be more full-featured than the former.
In any case, the question remains: Do markdown applications conflict with markdown philosophy? That is, does WYSIWYG contradict markdown?
According to the vrite.io site:
vrite is a collaborative, local-only markdown editor. Inspired by Notion and StackEdit.
The features include:
A Monaco-based editor, allowing markdown formatting through familiar UIs
Support for markdown tables
Embeds for CodePen, CodeSandbox, YouTube, etc.
Pasting in markdown content from anywhere else
Exporting in HTML, Markdown, JSON
StackEdit is a full-featured, open-source markdown editor. While it is somewhat similar to the Microsoft Word of markdown, it is not without its detractors. As part of its development, StackEdit is built atop PageDown, the engine used by Stack Overflow. Some people argue that this approach conflicts with markdown’s overriding goal of plain-text readability, since the WYSIWYG aspect might lead to markdown being overused and/or misunderstood. But others counter that markdown’s simplicity is itself an opportunity to make WYSIWYG markdown accessible, even if the two approaches seem contradictory at first glance.
One problem with markdown, though, is sharing it. Since it is plain-text, it needs an application or viewer to render it. However, a Microsoft programmer noted, “it’s hard to share Markdown files directly with others.”
That doesn’t have to be the case. Many good markdown editors support Pandoc. Pandoc is free and open-source. It’s a format-conversion tool that allows you to convert markdown into other document formats like HTML, PDF, ODT, etc.
So, how do markdown applications work? Typically, they allow you to edit markdown content in a separate view, with a preview area rendering it for you to see what it looks like when published. Most markdown applications combine the edit view and preview into a single view, which makes sense.
Markdown as a storage format
Markdown has some distinct advantages as a storage format, especially compared to proprietary alternatives. For example, templates can easily be updated to support design changes, while files aren’t locked to a specific application. If anything goes wrong, there are ways to fix things and continue moving forward. And perhaps most importantly, there’s no risk of obsolescence. All of this applies to any markdown editor, too.
But the fact that markdown is stored in plain text provides additional flexibility. For example, you can export markdown into another format simply by running it through Pandoc. With proprietary formats, you’re stuck working within them forever, assuming they don’t become obsolete.