Markdown Library ML-42 is a native macOS app for reading and editing markdown files already on disk, across as many folders and projects as you want, for $12.99 once.
iA Writer is a focused writing app for plain-text markdown, with Focus Mode, style feedback and a design pedigree few writing tools can match, sold once per platform, starting at $49.99 on Mac.
| Question | ML-42 | iA Writer |
|---|---|---|
| Interface | A sidebar of your folders, the document, and an inspector with the table of contents and a summary, ready on launch | Focus Mode dims everything but the current sentence or paragraph, an interface built to disappear while you write |
| Storage model | Plain .md files in your existing folders; nothing added | Plain-text markdown files in your folders too; no proprietary database |
| Works on existing folders | Yes, that is the product | Yes, and it is built around composing one document at a time |
| Platforms | macOS 26 or later, Mac only | macOS, iPhone and iPad, Windows and Android |
| Price | $12.99 once (introductory; it will rise), one purchase for Mac | $49.99 on Mac, $19.99 on iPhone and iPad, each platform sold separately |
| Writing tools | None. Reading and light editing, with no composition tools | Focus Mode, syntax highlighting by part of speech, Style Check for clichés and filler, Authorship tracking for pasted or AI-written text |
| Multi-project | Many folders open side by side, one search across all of them | Built around one document at a time |
| File watching and AI edits | FSEvents-based; reloads automatically when a file changes outside the app | No comparable pitch about external or AI edits appearing live |
| Track record | A new app | Apple Editors' Choice and four times "Best of App Store"; v8 shipped a Liquid Glass redesign for macOS 26 |
| Sync | None built in. Use whatever already syncs your folders | None built in either: your folders, your sync |
| AI-agent workflow | Built for it. File watching reloads a file when an agent edits it; on-device summaries; search skips build and dependency folders | Files are agent-editable too; the app's framing is composing prose |
| Learning curve | Small, by design: open a folder, read, edit | Small too. The discipline is in the writing tools rather than the setup |
What you see when you open each app
Open ML-42 and you are reading the folder you pointed it at straight away: a sidebar of folders and files, the document and an inspector, with nothing to configure first.
Open iA Writer and Focus Mode is ready to dim everything but the sentence or paragraph you are on, with syntax highlighted by part of speech, built to disappear around your writing. It is one of the most disciplined writing environments available, and it is built around composing a document. Browsing a folder of them is a different job.
The category's prestige name
iA Writer's reputation is real and worth stating plainly: Apple Editors' Choice, named "Best of App Store" four times, and its v8 release shipped a Liquid Glass redesign for macOS 26 with a Document Outline and Command Palette. Focus Mode, part-of-speech syntax highlighting, Style Check for clichés and filler, and Authorship tracking for pasted or AI-written text add up to a disciplined toolkit for writing prose.
ML-42 does not compete on any of that; it has no writing tools at all. If composing is the job, iA Writer is built for it in a way ML-42 is not trying to be.
A 4x price gap, for a different job
iA Writer is $49.99 on Mac, and iPhone or iPad is a separate $19.99 purchase, each platform sold on its own. ML-42 is $12.99 once, for Mac, an introductory price that will rise later.
The gap is less about features than about what each app is for. iA Writer is priced as a writing instrument you buy once and use for years of composing. ML-42 is priced as a reading and editing companion for files that already exist for other reasons: a repo, a docs directory, the context files an AI agent reads and writes.
Composing one document, watching a folder
ML-42 watches the files it is showing you with FSEvents and reloads automatically when an AI agent or another editor changes one on disk, so a folder that someone or something else is writing into stays current without you doing anything. iA Writer has no comparable pitch; its framing is a document you are composing.
ML-42 is a reader and editor for folders that exist for other reasons: repos, docs directories, agent context. If writing is the job, iA Writer may simply be the better fit. ML-42 competes when the files already exist and need to stay where they are.
- Writing is the job, whether essays, posts or documentation, and you want the most disciplined editor for it.
- You value style feedback on clichés, redundancy and parts of speech while you write.
- You want the same trusted writing environment on Mac, iPhone and iPad.
- Your files already live in folders that other tools and AI agents write into, and you want to read and browse across many of them.
- You want one purchase to cover your Mac, instead of a separate purchase per platform.
- You need a place to read and tidy markdown files that already exist more than a place to write new ones.
Also compare: Obsidian, Typora and Bear. All four side by side are on the home page.
Markdown Library ML-42
A native Mac reader and editor for the markdown in your repos and docs folders. No import, no vault.
Download on theMac App Store$12.99 once. Introductory price. It goes up later.