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Why Quick Look won't preview your .md file

The first thing every Mac user hits, and the two ways round it.

Select a .md file in Finder, press Space, and macOS shows you the raw source — hashes, asterisks and all. Quick Look has no built-in Markdown renderer, so it falls back to treating the file as plain text. Nothing is broken; the preview generator simply doesn't exist.

Two ways to fix it:

• Add a Quick Look plugin. QLMarkdown installs a Markdown preview generator via Homebrew. It works, and it keeps the Space muscle memory — but it needs Terminal, and macOS may need convincing to trust the plugin after each system update.
• Change the default app instead. Set a real Markdown viewer as the handler for .md files, and double-clicking gives you fully rendered output — with working links, syntax-highlighted code, math and diagrams, none of which a Quick Look preview does well even with the plugin.

To do the second: right-click any .md file in Finder → Get Info → expand Open with → choose MDHero → Change All. Every Markdown file on the Mac opens rendered from then on.

The honest version: Quick Look is unbeatable for a half-second glance, and a plugin makes it adequate. For anything you actually intend to read, a real viewer wins. There's a full breakdown in Quick Look vs MDHero.

Markdown viewer, markdown reader, or markdown editor?

Three words for the same job — and the one case where the difference matters.

People look for the same thing under a lot of names: markdown viewer for Mac, markdown reader, md viewer, macOS markdown app. The request underneath is identical — render the file instead of showing me its syntax.

The distinction that matters is reading versus writing:

• A markdown viewer / reader renders a file so you can read it — a README, a spec, a plan, pasted AI output. Launch speed matters more than features.
• A markdown editor for Mac is for writing — hours at a time, where themes, export formats and typing feel earn their keep. Typora and iA Writer are editors.

MDHero is both, weighted toward reading. It opens as a viewer, and the View / Split / Edit switcher is there when you need it — Split puts the editor and a live preview side by side, with line numbers and ⌘S to save. Native Apple Silicon, ~8MB, MIT-licensed, so it's also a genuinely open-source markdown editor if that's what you were after.

If you draft long documents in Markdown daily, a dedicated editor is worth paying for. If you mostly read and edit occasionally, this is the smaller answer — see Typora vs MDHero for that comparison in full.