MarsDawn

Viewing Markdown elsewhere, vs. MarsDawn.

If you already have VS Code, a browser or Claude Desktop open, reaching for one of them to glance at a Markdown file is reasonable. Here's what each one actually renders, and what it costs to get there, compared with opening the same file in MarsDawn.

VS Code's built-in preview

Press ⌘⇧V in VS Code and it renders the Markdown file in a built-in preview pane, free, with nothing to install. As of VS Code 1.121 (May 2026), that preview also renders Mermaid diagrams natively — Microsoft folded a Mermaid extension into VS Code itself, so this used to need a separate extension and no longer does. What it doesn't do: it's a preview pane inside an editor, not an editor built for reading — the pane sits next to a file tree, a terminal and every other panel VS Code can show, and VS Code itself is an Electron app you install as a whole development environment, not something you open to read one file.

A browser extension for local files

No single browser extension dominates for reading a local .md file: Local Markdown Viewer, Markdown Viewer, MarkView and others all do roughly the same thing, and none is a default. Every one of them needs the same extra step before it can open anything: turning on "Allow access to file URLs" for that extension, because browsers block extensions from reading file:// pages by default. That's a permission you grant once per extension, and it's easy to forget you did it, or why. Once it's on, the file renders in a browser tab, which means running a full browser to look at one file.

Claude Desktop's file preview

Claude Desktop shows a file that's already in a Project or a conversation. What it isn't built for is browsing arbitrary files on disk — what you can look at is what the conversation already holds, not a folder of notes you keep open beside your work. Anthropic's own list of the document types you can upload is PDF, DOCX, CSV, TXT, HTML, ODT, RTF, EPUB, JSON and XLSX: Markdown isn't on it.

A browser engine to read one file

VS Code is an Electron app: a bundled Chromium and Node.js runtime, not a native Mac app. The browser-extension route runs inside an actual browser. Either way, viewing one Markdown file means a full browser engine is running to show it. MarsDawn is a native AppKit app: no bundled browser runtime, it opens any local file directly, with no extension to install or permission flag to remember.

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