Read markdown as rich documents, right in your browser.

Double-click a .md file and read it like a document, not source code.

Install for Chrome · Website · Changelog

Features

Reading

• Opens local .md and .markdown files by double-click
• Contents rail built from your headings, with click-to-jump and live position
• Floating or fixed sidebar, whichever suits the document
• Fullscreen mode that hides the browser chrome
• Read-only — your file is never modified

Appearance

• Six themes — White, Paper, and Dawn for light; Carbon, Ink, and Onyx for dark
• Custom themes — build your own from twelve tokens, save as many as you like
• Follows your system theme, remembering a preset for each mode
• Font, text size, and line spacing controls
• Adjustable content width, from a narrow column to full screen

Markdown

• GitHub Flavored Markdown — tables, task lists, footnotes, strikethrough, automatic links
• Syntax highlighting with a language label and copy button
• Math with KaTeX, inline and block
• Mermaid diagrams
• SVG and safe embedded HTML

Privacy

• Local-first — nothing is uploaded, no server, no account
• Every document sanitized before it renders
• Free and open source

After install

A setup guide opens automatically when you install Mark and walks you through the steps below. This is the same thing, for reference.

1. Allow access to local files

Chrome blocks all extension access to local files by default, so Mark cannot read your .md files until you turn this on.

1. Go to chrome://extensions
2. Find Mark and click Details
3. Turn on Allow access to file URLs

Mark only reads files you open, and nothing leaves your browser.

2. Set Chrome as the default app for Markdown

macOS — Right-click any .md file → Get Info → Open with → Google Chrome → Change All

Windows — Right-click any .md file → Open with → Choose another app → Google Chrome → check Always use this app

Then double-click any .md file.

Supported browsers

Chrome, Edge, Brave, Arc, Opera, and similar browsers.

Firefox and Safari support is planned.

Development

pnpm install
pnpm dev      # build and watch
pnpm build    # production build
pnpm package  # production build, zipped into releases/

Load the unpacked extension from extension/dist at chrome://extensions with Developer mode on.