Skip to content
Redlines

Markdown, beautifully. See every change.

Redlines is a free, open-source Markdown editor for Mac, Windows and Linux. It opens what you and your AI tools write as beautifully rendered documents, and shows every change, yours, your colleagues’ and your AI’s, for you to accept or reject.

Read the design specView on GitHub

Not released yet. The design and the format are open for feedback on GitHub.

plan.md

Launch plan

We will ship the new importer in MarchApril, after the security review. The old exporter stays as it is.

Claude for Ada
Replaced “March” with “April”
Bo
Who signs off on the security review?

Ada added “new”. Claude, working for Ada, suggested “April”. Bo deleted a sentence and asked a question.

Markdown is the document format of AI.

Answers from ChatGPT and Claude, plans and reports from agents, READMEs and specs all arrive as .md files, and most apps show them as code. Redlines shows you a beautifully rendered document.

  • Open any .md file and read it formatted, with tables, math and diagrams.
  • Paste from web pages, Word or Google Docs and get clean Markdown.
  • Copy into Word or Google Docs and keep the headings, tables and fonts.

report.md in a text editor

## Findings

| Arm     | n  | Response |
| ------- | -- | -------- |
| Placebo | 42 | 18%      |
| Drug    | 40 | 47%      |

**Next:** confirm in a *larger* cohort.

report.md in Redlines

Findings

ArmnResponse
Placebo4218%
Drug4047%

Next: confirm in a larger cohort.

See every change.

When a colleague or an AI edits your document, each change shows who made it and when, and you accept or reject it, like Track Changes in Word or Suggesting in Google Docs. It is all saved in the plain Markdown file.

  • Accept or reject one change, everything from one person, or all at once.
  • Comment threads in the margin, with replies and @mentions.
  • AI agents suggest edits in their own name, or edit directly if you prefer, with a record you can undo.
  • Use the Claude or ChatGPT account you already have, your own API keys, or a local model.
protocol.md

Interim results go to the safety board next quarterby October 31.

Claude suggested this for Ada

How Redlines compares

Redlines as designed. Other products as of October 2026, from their documentation. VS Code includes the Live Share, GitHub Copilot and Quarto extensions.

FeatureRedlinesWordGoogle DocsNotionVS Code
Edits Markdown files
R Markdown and Quarto
Tracked changes (suggestions)
Comment threads
Accept or reject by person
Tracked changes stored in the Markdown file
Changes and comments merge in git
Full edit history, stored in the file
Live collaboration with people
Live collaboration with AI
AI agents suggest changes in their own name
Word files with tracked changes, in and out
Desktop app for Mac, Windows and Linux
Embeddable editor component
Free and open source

Live collaboration with AI means an agent that works in the document as itself. In Word and Google Docs, the AI edits only when asked, and its edits count as yours.

Wherever documents get reviewed

Tracked changes and comments are how contracts, regulated documents and papers get written. Redlines keeps them in plain Markdown, which every tool can read.

  • Legal

    Drafting and negotiation, where every change must be visible and attributable, and the full history of a negotiation can be replayed.

  • Pharma and healthcare

    SOPs, policies and other controlled documents, with review and approval cycles.

  • Academia

    Scientific manuscripts and responses to reviewers, co-authored with figures, captions, citations and cross-references, and usually sent to the journal as a Word file.

  • Data science

    R Markdown and Quarto documents, reviewed the way prose is, without leaving the source format.

For developers

  • Plain Markdown files

    Changes and comments are stored in the file. GitHub, VS Code, pandoc and Quarto show the latest version and hide the markup.

  • Made for git

    Tracked changes merge with git. When Redlines’ own data conflicts, keeping both sides always resolves it, by hand, by an AI or automatically.

  • Full history, if you want it

    Keep only the current version, or every edit, so any earlier version can be replayed. No sidecar files, no backend.

  • Agents through MCP

    Claude, Codex and other agents edit through Redlines’ tools, so their work arrives as reviewable changes.

  • A component for your app

    The editor, with tracked changes and comments, as a React component that takes on your app’s look.

  • An open format

    A documented file format, and MIT-licensed tools that read and write it: a TypeScript library, a command line and an MCP server.

Redlines is being designed in the open.

The design spec, the file format and the research behind them are on GitHub. Feedback on the idea, the format or the features is welcome.

Read the design specRead the format

Download

Coming soon

Redlines isn’t released yet. It will be available for macOS, Windows and Linux.

  • macOS

    • Apple silicon and Intel

  • Windows

    • Installer, x64

  • Linux

    • AppImage, x86-64
    • Debian and Ubuntu, x86-64
Follow development on GitHub