Press Space on a Markdown file and read it

Press Space on a Markdown file in Finder and read it rendered. MD Flow adds a real Markdown preview to Quick Look on Mac, free with the app.

On a Mac, pressing Space on almost any file shows you the file. Press it on a .md and macOS shows you the source: # Heading, **bold**, backticks, the lot. The system declares Markdown a kind of plain text, hands it to the plain-text previewer, and that previewer does exactly what it was built to do.

MD Flow replaces that preview. Install the app and Quick Look renders Markdown the way the app does — headings as headings, tables as tables, callouts with their colours, math as math. Select a file in Finder, press Space, read it, press Space again. It is free, it comes with the app, and there is nothing to configure.

#Install the app, get the preview

There is no separate download, no Homebrew step, and no xattr -cr to get past Gatekeeper. MD Flow ships from the Mac App Store; the preview extension is part of it and macOS registers it when the app is installed.

If Finder is still showing the old preview right after installing, open the app once — macOS registers extensions on first launch. Extensions can also be toggled in System Settings under Login Items & Extensions, so if you have previously turned Markdown previewers off, it will be there.

#What it renders

The same renderer as the app, so what you see with the spacebar is what you see when you open the file properly:

Headings, paragraphs and lists with real reading typography
Tables, task lists, and syntax-highlighted code blocks
Callout blocks (> [!note], > [!warning], …) in Obsidian style
KaTeX math, inline and display
YAML frontmatter as a tidy metadata header, not a wall of dashes

#What it deliberately doesn't do

A preview extension is not a small version of the app, and pretending otherwise is how these things end up slow and broken. Three limits:

Mermaid diagrams fall back to highlighted code. The Mermaid library is about 2.5MB, which would be most of the extension's weight, and a preview that has to parse that much JavaScript is one macOS kills for being slow. Open the file in MD Flow and the diagram renders.
Wikilinks stay as text. Resolving [[Another Note]] means walking the folder, and a preview extension is handed one file, not its neighbours.
Local images are best-effort. Same reason — the extension is granted the file it was asked to preview, so a sibling image may be unreadable. It leaves a gap rather than failing the whole preview. In the app, where the folder is connected, images load normally.

#Then there is the rest of the folder

The spacebar is for one file. When what you actually have is a folder of thirty — a documentation tree, an Obsidian vault, a directory your AI assistant writes into — pressing Space thirty times is not browsing. That is what the app is for: a folder tree beside a rendered preview, with search, recents and a table of contents. See browsing a folder of Markdown.

MD Flow is free on the App Store for Mac, iPhone and iPad. Pro is a one-time $7.99 unlock — unlimited folders, search inside documents, email drafts and PDF export — and never a subscription.