macOS 14+ · one-time $1.99 · source on GitHub · no account
Open a 32 MB Markdown report like a two-line note. Keep several documents open without putting a browser engine behind every window. Diagrams, formulas, front matter and tables are already rendered when the file appears.
Markio in 50 seconds · sound on
Why it feels different
The parser reads your file as bytes and CoreText typesets only the lines on screen. Nothing is converted to HTML on the way, so there is no browser to start and no second copy of your document living inside a renderer.
The biggest document the benchmark throws at it parses in 69 ms, and the first screenful is drawn in well under a millisecond. Length stops being something you think about before double-clicking.
Opening an 8 MB report costs Markio 2.8 ms of processor time. Three other native Markdown viewers for the Mac, given the same file on the same machine by the same harness, spent 64, 122 and 123 ms on it, and every one of them held more memory doing it — from half as much again to thirteen times as much. Each of them hands the document to a browser engine first.
No account, no telemetry, no font fetched at runtime, no diagram sent away to be drawn. Nothing about your reading is recorded anywhere, because there is nowhere for it to go.
Release build on Apple silicon. The tools that produced these numbers ship with the source, so you can repeat them on your own Mac.
Always live
Another app rewrites the file and the window follows: the same window, redrawn with the new text the moment the file changes.
Nothing to reload and nothing to reopen. Every time the file changes, the window redraws on its own.
A report a script or an agent regenerates updates in front of you, run after run.
There is no HTML rendering of the document to rebuild, so a reload costs what one screen costs.
Markdown extensions
Formulas, Mermaid diagrams, YAML front matter, task lists, footnotes, syntax-highlighted code, terminal colour and rich tables — rendered together in one native document.
20+ diagram types
Flowcharts, sequence diagrams, state machines, ER, C4, Gantt, mindmaps, Sankey, treemaps and more — drawn by Markio itself, entirely offline.
Rich tables interface
Click a heading to sort by that column. Type in the filter row to keep only matching records. Read aligned numbers, wide reports and HTML tables without moving the data into a spreadsheet.
Built-in file comparison
Compare the open document with an earlier version. Read additions and removals inline, or put both versions side by side and scroll them together. You compare the document as a reader sees it, not two walls of Markdown source.
Presenter mode
Markio turns the document's own thematic breaks and headings into slides. There is no export, duplicated deck or second file to keep in sync.
Zen mode
Hide the outline, document map, find bar, controls and window chrome, then give the display to the page. Press Escape and the window returns exactly as it was.
And before you open the app
Markio installs a Quick Look extension, so the preview you already reach for shows the real document — diagrams and formulas included. No window to open, no app to switch to, nothing to close afterwards.
An actual Quick Look window — the Space bar, and nothing else was opened. The "Open with Markio" button is macOS's own.
Instead of what
Here is honestly where each one leaves you.
Source available
All of Markio's source is public on GitHub. That is not a footnote at the bottom of the page — it is the reason you can believe the rest of it. Every other reader asks you to take its word. This one hands you the evidence and invites you to go looking.
"Nothing leaves your Mac" is a sentence any app can print on a website. Here you can read the code behind it — and the build gate fails outright if a reference to WebKit or JavaScriptCore ever reaches the sources.
The harness that produced 0.3 ms and 69 ms ships with the source. Clone the repository, run deno task bench, and get the numbers on your own Mac instead of mine.
A Swift toolchain and one command give you a working app for nothing. If Markio does not do what this page promises, you can find that out without spending anything.
The licence lets you build Markio for your own use, today and later. An app you can rebuild yourself doesn't vanish when a store delists it or a developer loses interest.
Then the obvious question
The part that building it yourself does not give you — the app already assembled, trusted by the system and keeping itself up to date.
For IT teams
Markio has no server, no account and no licence key, and nothing to configure on its side. There is no setting to lock down, because the app has nothing to send. It needs macOS 14 or later and nothing else. Its App Store privacy label reads "Data Not Collected".
The app and its Quick Look extension run in Apple's App Sandbox without the network entitlement, so the system refuses any connection they might try to open. Check it on any Mac: codesign -d --entitlements - /Applications/Markio.app
The sandbox lets Markio read a file only after someone opens it or picks it in a panel. It never writes a document it opens. Apart from its own settings, the one file it creates is a PDF someone exports, in the place they choose.
Everything the app runs is public on GitHub, and the build fails if WebKit or JavaScriptCore ever reaches the sources. A review does not have to take the developer's word for anything.
Deployment
A question before a rollout? Open an issue on GitHub and the person who wrote the app will answer it.
No subscription, no account, no upsell inside the app. macOS 14 or later.
No. Markio opens documents to read them and never writes a file it opens. Keep editing in whatever you like — the window redraws every time you save.
No. There is no account, no telemetry and no fetched font. Links open in your browser only when you click one.
It keeps its source instead of being guessed at. A formula outside the supported subset, or a diagram type not yet drawn, stays visible as the text you wrote.
Open an issue on GitHub and you will get an answer from the person who wrote the app. Apple refunds App Store purchases on request, through Report a Problem — and I would rather fix the reason than keep the money.
Already reading with Markio?
If Markio has earned its place on your Mac, a rating or a two-line review on the Mac App Store tells other people it is worth trying. If something is wrong instead, tell me first — I would rather fix it.