GS VectorShell Twinmark
1.0 Now in the Microsoft Store · see what's coming next

Markdown, two ways at once.

Write the markdown, or the page it becomes, or both side by side. Twinmark keeps the two in step as you type and rewrites only what you change, for documentation that ends up on GitLab and GitHub.

Get it from the Microsoft Store Take the tour

Free trial · Windows 10 (version 1809 or later) and Windows 11, 64-bit · No account needed

Twinmark with a release guide: markdown in the left pane, the same document formatted in the right pane.
Recorded in Twinmark 1.0. A section typed as markdown on the left appears formatted on the right; a sentence typed on the right, with **bold**, appears as markdown on the left; a task ticked on the right is ticked in the markdown.

Two panes, one document

Type in either pane. The other keeps up.

The markdown is the document. Change it as text, or as the finished page, and Twinmark rewrites only the lines you touched, so your spacing, list markers and tables stay just as you wrote them.

What's in 1.0

Everything a long document needs

From the first heading to the export, with checks that know how GitLab and GitHub will show it.

Two panes, in step

The source and a visual editor side by side, or either one on its own. The block you're editing is highlighted in both.

Checked for GitLab and GitHub

Broken links, headings out of order, missing alt text, hard sentences, and markdown the sites show differently, with fixes.

An assistant that asks first Optional

Shorten, simplify, proofread or review, on your own computer or with your own key. Nothing changes until you accept.

Find your way

An outline, a command palette, find and replace, templates, and a table of contents that keeps itself up to date.

Your work is safe

Version history, recovery of unsaved changes after a crash, and Auto Save if you want it.

Export when you share

HTML, PDF and Word, with your pictures included. Saving keeps each file's encoding and line endings.

Two monitors, two themes

Give the visual pane a window of its own on a second screen. Light or dark, and sharp at every scale.

Checked as you write

Know how it'll look on GitLab before you push

Twinmark reads your markdown the way GitLab and GitHub do, and tells you when they won't show what you see. Most problems have a fix one click away.

  • Links to headings that aren't there
  • Headings that skip a level, pictures without alt text
  • HTML that GitLab removes, and what to use instead
  • Reading level, long sentences and the passive voice
Watch the checks at work
Twinmark's problems panel under the two panes, after its fixes: the link now goes to the Environments heading, and the underline is written the way GitLab keeps it.

Optional, and on your side

An assistant that runs on your computer

Download a model once and the assistant works offline, with nothing you write leaving your computer. Or use OpenAI or Azure OpenAI with your own key, once you've agreed to it.

  • Shorten, expand, simplify, make formal, fix spelling
  • Review the writing, the structure and accessibility
  • Every suggestion shown as a change you accept or discard
  • Its changes are never saved for you, and stay marked as its own
See it simplify a sentence
Twinmark's assistant panel beside the document, after the long sentence it simplified was accepted into the document.

Made for Windows

Light or dark, like the rest of your desktop

Twinmark follows your Windows theme, or the one you choose, and stays sharp on every monitor.

Twinmark in its light and dark themes, a line moving between them: the same release guide, with a table toolbar over a table in the visual pane.

Private by design

Your documents stay on your computer

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accounts to make. Open a file and start writing.

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ads. You buy Twinmark once, after a free trial.

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trackers or analytics, in the app or on this website.

The details are in the privacy policy.

Stay tuned · Twinmark 1.1

Equations, diagrams and more are on their way

The next version is taking shape: equations you type as they look, diagrams you change by clicking them, a Files panel, and a find and replace that works in both panes.

  • Equations
  • Mermaid diagrams and charts
  • Files panel
  • Find and replace in both panes
  • Formatting bar
  • Word count
See what's coming

Try it free

Twinmark is in the Microsoft Store with a free trial in which everything works, the AI assistant and the second window included.

Get it from the Microsoft Store

Windows 10 (version 1809 or later) and Windows 11, 64-bit.