Nethermark
A small Markdown editor for your web app.
Nethermark is a small Markdown source editor built on CodeMirror 6. Use it from JavaScript, as a web component, or in React. Versions are 0.x, so the API can still change.
v0.3.2Nov 2, 2026Free and open source (MIT)
npm install @netherstone/nethermarkimport { createMarkdownEditor } from "@netherstone/nethermark";
const editor = createMarkdownEditor({
parent: document.querySelector("#editor")!,
doc: "# Hello",
onChange: (doc) => console.log(doc),
});What it does
- All of MarkdownCommands for all of CommonMark and GitHub-flavored Markdown, with toolbar buttons and shortcuts for the ones people use most.
- Plain JavaScript, HTML or ReactUse it from plain JavaScript, drop <nether-mark> into a form in HTML, Vue, Svelte or Angular, or use the React component on React 18 or 19.
- A live previewShows the Markdown rendered by whichever renderer you pass in. HTML is sanitized by default, and the preview scrolls with the editor.
- ThemesIt ships with Netherstone's Light and Dark themes. Colors, labels and icons can all be replaced, and it keeps its look on pages that use Tailwind's CSS reset.
Concept
The repo was set up under the same GitHub organization as Netherstone.
0.1.0 went to npm with the editor, its toolbar and shortcuts, and support for adding your own Markdown syntax.
0.2 added the <nether-mark> web component, the preview, touch screen support and the React package. Every label and icon can now be replaced. 0.3 followed the same day with the Netherstone app's Light and Dark colors, and 0.3.1 added multiple cursors.
0.3.2 made a height set on the editor hold, so the text scrolls inside it instead of being cut off.
The Markdown converter on netherstone.app needed a source editor next to a live preview, and Netherstone's own editor is a rich editor, so it couldn't be used there. I wrote a small editor on CodeMirror 6 whose commands read the Markdown syntax tree, so formatting toggles cleanly and leaves code alone. I published it on its own under MIT so anyone can use it. The converter was its first user, and the demo page the second.
How it's built
Nethermark is a pnpm monorepo with two packages. Commands are tested on CodeMirror's editor state alone, without a browser. Playwright runs the editor in Chromium, Firefox and WebKit, and the React component on React 18 and 19. Releases are versioned with Changesets and published to npm with provenance.