Mark
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Agents write Markdown. Mark draws it.

Mark opens the file your agent is writing and renders it as it saves: tables, 32 kinds of diagrams, math, callouts. ⌘D shows what changed since you last looked.

Download Markfor macOS · Apple silicon · v2.8.2 Download Markfor Windows · x64 · v2.8.2 Build Mark from sourceLinux · no packaged build yet

Mac App Store macOS Windows All downloads

Free, MIT · same editor, two editions · What’s the difference?

q3-review.mdReloaded

Q3 review — growth

Written by the agent from analytics.csv and billing-export.csv

Funnel

Search → Visitors: 520Ads → Visitors: 340Referrals → Visitors: 240Visitors → Signed up: 690Visitors → Bounced: 410Signed up → Activated: 470Signed up → Dormant: 220Activated → Pro: 180Activated → Free: 290Search 520Visitors 1100Ads 340Referrals 240Signed up 690Bounced 410Activated 470Dormant 220Pro 180Free 290

Targets

MetricQ2Q3Δ
Signed up540690+28%
Activated350470+34%
Pro140180+29%
Note
Ads spend paused in week 38.

Where the time went

Where the time went42%26%20%12%WritingReviewBuildQA
What the agent savedWhat you see in Mark
⟵ drag
↻Live reload

Every save, in placeScroll position stays where you were.

⌘DChanges

See what the agent touchedAgainst a snapshot taken before each reload.

32Diagram types

Drawn in the pageFlowchart to sankey, in your theme’s colours.

0.4 sNative

Small and quick≈ 30 MB on disk, the system WebView.

¶ 01

Watch your agent write.

Every save on disk reloads the tab in place, keeping your scroll position, so you can follow a long pass and step in when it finishes. ⌘D shows exactly what the agent changed, against a snapshot Mark takes before every reload.

plan.mdReloaded
A plan document beside the folder tree, with Recent, Pinned and the page outline

Connect your agent

The home screen connects your agent with one click — or paste this prompt into CLAUDE.md, AGENTS.md or any system prompt your agent reads.

Prompt for your agent 
When you produce a plan, spec, report, or any document longer
than ~50 lines, write it to a .md file and open it for the user:

    open -a Mark <file>.md

The user reads and edits it in Mark, which reloads the file when
it changes on disk. When the file changes, read the new version:
the user left corrections inline. Treat the diff as your next
instruction.

¶ 02

32 kinds of diagrams, drawn as your agent saves.

Flowcharts, sankeys, Gantt charts — a plain ```mermaid block in the Markdown, drawn in the page in the colours of the theme. Pick a theme and watch the wall follow:

```mermaid → drawn on save
Flowchart```mermaid
Sankey```mermaid
Pie```mermaid
Venn```mermaid
Radar```mermaid
Kanban```mermaid
Gantt```mermaid
Swipe · 4 of 32 types

See all 32 diagram types in every theme →

¶ 03

Write in the finished page.

Headings, tables, task lists, footnotes, callouts and front matter look done while you type — and the rest of the page keeps up.

  • Split View

    The raw Markdown beside the page when you need it; the rendered page itself is the editor.

  • Copy it clean

    Copy as Markdown, HTML, plain text or structured text that keeps paragraphs, bullets, links and tables readable wherever you paste them.

  • A large release-pipeline diagram open in the fullscreen viewer, zoomed in

    Open anything full screen

    Any diagram or wide table opens here, with zoom and pan and a sticky header for tables.

  • Print & PDF, each direct

    ⌘P opens the system print panel directly; Export to PDF writes the file through a save dialog, without the print panel — on macOS and Windows.

  • A plan document in the light theme The same plan document in the dark theme

    32 themes, light and dark

    Light and dark members, one title-bar button apart — Paper, Ink, Docs, macOS and more; diagrams can follow, or pin their own look.

  • Diagrams as pictures

    Copy as image, or save as PNG or SVG in the theme’s colours — from the diagram’s corner panel, the context menu or the full-screen view.

¶ 04

Small and native.

Mark renders with the system WebView — WebKit on macOS, WebView2 on Windows — instead of shipping its own browser engine.

Memory with the same rich document open

  • Marknative · system WebView ≈ 310 MB
  • An Electron notes appsame document ≈ 400 MB
  • An Electron code editorsame document ≈ 1 GB
First window
≈ 0.4 s
On disk
≈ 30 MB
Plain document
≈ 150 MB
4,100-line file
≈ 3 s to open

Measured 2026-10-15, one Apple silicon Mac, Mark 2.3.0 — your numbers will differ; a rich document means Mermaid diagrams, KaTeX math and a table open together.

¶ 05

Get Mark

Free and open source, MIT licence. No account, no analytics, no telemetry in the app.

  • macOS: Developer ID signed and notarized by Apple; updates arrive through the in-app updater or brew upgrade --cask mark.
  • App Store: the App Store edition is 2.1.17 today; its next update brings 2.5.0. When does it catch up?
  • Windows: the installer is not code-signed yet, so SmartScreen shows “Windows protected your PC” — choose More info, then Run anyway.

Two editions, the same editor. Homebrew/download adds pandoc export, insert screenshot, the default-Markdown-app setting, git diff, a local live server for agents and the in-app updater; the App Store edition is sandboxed and reviewed by Apple. See the full table.