As of 2026-09-14. Engine: MarkEngineV3, Mardo's own, by Floof Logic. Full, auditable source: ENGINEERING.md on GitHub · Numbers: /benchmarks/

Engineering

What MarkEngineV3 does, and what that buys. The numbers these choices produce are in Benchmarks; the full, auditable source of both parts is ENGINEERING.md on GitHub.

MarkEngineV3

Mardo runs on MarkEngineV3, a complete document and rendering engine built by Floof Logic from the ground up. It contains no web view, no JavaScript engine, and no third-party runtime. The parser, the math, the diagrams, the HTML and PDF output, the updater, the license verifier, and the AI tooling are all MarkEngineV3, all Floof Logic's own work. This is unusual, it was expensive to build, and it is the reason every number on the Benchmarks page exists: an engine written for this one job, with nothing borrowed in the hot path, can be held to standards a general-purpose stack cannot reach. Everything below is MarkEngineV3.

The file is the document

Your words live in an ordinary Markdown file on your disk. Opening it never rewrites it, and only an explicit Save writes it back. Viewing, rendered editing, and source editing are three presentations of the same bytes, so nothing is normalized behind your back and copying returns exactly what you wrote. Undo is instant whether you removed one character or sixteen megabytes, and nothing you have typed is ever discarded to make that work. There is no vault, no import step, no database, and no hidden copy of your document anywhere.

Size stops mattering

MarkEngineV3 renders only what you are looking at. Opening a file, and jumping anywhere inside it, never does an amount of work that grows with the file, so a one-kilobyte note and a fifty-gigabyte log reach the screen in the same few milliseconds and hold the same small, steady memory. Drop the scrollbar halfway through a multi-gigabyte file and the text under it is on screen in a single frame while the surrounding structure settles behind it. Search is the one thing that must read every byte, and it does so at the speed of the disk with a working Cancel. The measured figures are in Benchmarks.

One engine, every surface

The window, the Finder Quick Look preview, the Finder thumbnail, the HTML export, the PDF, the printed page, and the clipboard are all produced by MarkEngineV3 and the same themes. A preview agrees with the window, and the window agrees with the printed page, because there is only ever one interpretation of your document.

Nothing in your document can run

Because there is no web view and no JavaScript engine anywhere in the product, a document has nothing it could execute: not HTML, not scripts, not code fences, not math macros, not diagram callbacks. Math, diagrams, and raw HTML are rendered by Floof Logic's own bounded implementations, which show unsupported input as plain source rather than guessing. Remote images are the only thing a document can fetch from the network, over a hardened transport with no cookies, no credentials, and a global off switch. Documents never leave your Mac. The shipped application carries no web view, no JavaScript engine, and no third-party runtime; MarkEngineV3 is the whole of it, and that is verifiable in the binary itself.

It behaves exactly like the Mac

Every ordinary key does what the Mac's own text editing does, and Floof Logic proves it rather than asserting it: motion, selection, deletion, word and paragraph commands, international input, and the standard shortcuts are checked against the Mac's own text system across 54,065 cases with zero divergences and no exceptions granted. People bring years of muscle memory to a Mac text field; MarkEngineV3 earns that memory instead of approximating it.

You are not the only writer anymore

Coding agents, formatters, and other tools now save the file you are reading, often several times a minute. Mardo treats that as normal. When another writer saves, Mardo adopts the change in place, keeps your scroll position and your unsaved edits, and marks the one spot where your work and theirs genuinely collide, with no dialog and no reload flash. Timewarp keeps every state the file passed through while it was open and lets you step back through them where you are, without writing anything to disk. The rest of the field reloads over you, prompts you on every save, or merges and sometimes loses your work.

Where Mardo is measurably ahead of the field

Each line pairs a Mardo capability with the field's own published position. Competitor claims were read from their sites, READMEs, and (for Downright) its FEATURE-MATRIX.md, PERFORMANCE.md, STATUS.md, and ARCHITECTURE.md on 2026-09-11, with repo activity re-checked 2026-09-14. No competitor was installed; every competitor statement is the vendor's own. The numbers cited are in Benchmarks.

1. Size never degrades it. A 50 GiB file and a 1 KiB README reach the screen the same way. Downright, the closest native project, lays out whole documents below a 5 MB threshold and rebuilds on a mode switch, by its own PERFORMANCE.md and STATUS.md. Obsidian's own guidance is that it "degrades above 1 MB." MarkEdit advertises editing "10 MB files easily"; QuickMD advertises "10,000+ lines." Mardo's published ceiling is 50 GiB.

2. A published first-paint number. No competitor publishes one. Mardo's is 3 to 5 ms from 1 KiB to 16 MiB, dated and re-run before releases.

3. Editing proved against the Mac itself. 54,065 cases, zero divergences, no exceptions. No competitor publishes a comparable fidelity result.

4. No web runtime. Of seventeen surveyed products, Typora and Obsidian are Electron; Marked 3 is WebKit; QLMarkdown runs MathJax and Mermaid JavaScript inside Quick Look; pluk, Clearly, and QuickMD render through WKWebView; Marky and MRDown are Tauri; PreviewMD and showmd bundle a JavaScript engine. Mardo runs none, so nothing in your document can execute.

5. Quick Look that is native, selectable, live, and uncapped. Mardo's preview appears in about 57 ms at any file size and follows external saves in place. Downright's STATUS.md caps its Quick Look at 2 MB with an "Open in App" fallback and targets under 400 ms with no automated measurement; QLMarkdown's preview is a WebKit page running JavaScript.

6. Coexistence with another writer, proved. Follow Live Edits across 24 scenarios; Timewarp writes nothing. The field reloads, prompts, or merges heuristically.

7. Search at memory bandwidth. Gigabytes per second over a multi-gigabyte corpus. No competitor publishes a search-throughput number.

8. A verification record behind every claim. Only Downright publishes a performance document at all, and it labels its launch, scroll, and memory rows manual gates (PERFORMANCE.md, read 2026-09-11). Mardo's performance gate runs against a hard per-frame limit, and every number on the Benchmarks page has a dated gate behind it.

No web runtime, across the field

Read 2026-09-11 from each product's own description; repo activity 2026-09-14. MarkEngineV3 is Mardo's own; the column below is each competitor's own account of its stack.