rapier

Rapier

Fast, offline Markdown editor and note-taking app for Android, Web and Windows. Write notes, make Mermaid diagrams, draw editable SVG and paint with watercolor or MyPaint brushes. Keep text and pictures together in plain Markdown. Import Word and PDF; export Word, PDF, text and offline HTML for free. No ads or tracking. Collaborate online with AI agents over MCP and WebMCP, or share a file with the full editor inside.

• On the web: rapier.website. Add it to your home screen; let the first load finish before going offline.
• As a file: download rapier.html and open it in a browser. Two smaller builds sit beside it: rapier-document.html, the editor without Draw, Paint, Notes and the JPEG XL encoder, and rapier-reader.html, a read-only reader.
• On Android: the Rapier app on Google Play. It has no Internet permission. Optional Google Play asset packs download on first use, then work offline.
• With an agent: the Claude plugin, ChatGPT or another MCP client at https://mcp.rapier.website/mcp; Muse at https://mcp.rapier.website/muse.

What it does

• Write. Edit the page or the Markdown source; source you did not touch stays byte for byte. Tables, checklists, callouts, footnotes, LaTeX equations, Mermaid diagrams, a table of contents, find and replace, compare, text-to-speech, right-to-left, light and dark. Add comments and suggested edits.
• Pictures. Stored inside the .md file; new rasters as JPEG XL from Rapier's own encoder. Text wraps around a picture's shape.
• Draw. Editable SVG: freehand pen, pressure brush, shapes, arrows that stay attached, text and typographic art.
• Paint and Water. MyPaint brushes, smudge and blend; Water, watercolour whose pigments mix, flow and dry on textured paper.
• Notes. One Markdown file per note: colors, pins, checklists, voice recordings, links, history, and search that reads text in pictures. Import from 15+ note apps. Android adds reminders and a home-screen widget. Backup as a zip; encrypted sync to your own Cloudflare R2 bucket with an existing storage key.
• Files. Opens Markdown, text, code, Word and PDF. Saves Markdown and never overwrites a file changed elsewhere. Export Word, PDF, text and a static offline HTML page for free. A .rapier.html file carries the full editor and document together: edit, comment or suggest changes offline, then send the file back.
• Privacy. Editing and local Notes run on your device without analytics. Connected agent workspaces use hosted storage. Remote pictures load only when you allow them. Back up browser-stored notes from Notes settings → BACKUP.

For agents

1. Work together live. Connect to https://mcp.rapier.website/mcp, then call open to share one document with the person.
2. Deliver an offline editor. Run npx rapier-html notes.md to put the document and editor in one HTML file (rapier-html).
3. Embed in your app. Install rapier-embed; mount the editor or reader, with your app's agent over WebMCP in the editor.
4. Keep portable Markdown. Use rapier-markdown-kit for pictures, editable SVG drawings and layout in one .md file. Respect Will/1 keep, append and edit regions.
5. Encode JPEG XL. Install rapier-jxl to encode pixels, photographs and existing JPEGs in JavaScript.
6. Host the door. Run rapier-server over your own folder or S3-compatible bucket.

The agent edits live, beside the person or while they are away. Rapier shows the agent's presence and its changes. Tap a change to see what was there before; undo anything while keeping later edits. The agent can deliberately show a diff with show {target:"comparison"}.

The agent reads the passages it needs and changes exactly what it read. The person's typing comes first. Agents draw editable SVG diagrams and paint with the same brushes the person uses. The Will marks what an agent may edit, only add to, or must leave alone (Will/1). llms.txt, AGENT-TOOLS.json, the agent guide and the skills describe the tools and workflows.

Start with open, then read the passages or fenced blocks you need. Use edit with the returned revision and unique exact text; one batch becomes one undoable act. Drawings, painting and comments use the same fenced text surface. show presents work, asks a question or requests an editor action; export returns an independent file. read {search:"words"} finds Notes in the person's configured store. Read the rapier://guide resources for the full contracts. Save and export receipts name what was kept.

claude plugin marketplace add jackskip22/rapier-plugins && claude plugin install rapier@rapier
npx rapier-html notes.md                            # one offline page: the editor with the document inside
npx rapier-html revised.md --compare original.md   # the edited document, opened with its before for comparison
npm install rapier-markdown-kit                     # read, write and render the Markdown without the editor (MIT)

Any MCP client connects at https://mcp.rapier.website/mcp with no account; in ChatGPT, add it in developer mode (OpenAI's guide). export keeps exact Markdown, the offline editor, text, a web page, Word or PDF, independent of the hosted workspace, which expires after 30 idle days. Data handling: rapier.website/privacy.

In your own app

npm install rapier-embed mounts the document editor, or with build: 'reader' the read-only reader, in your page. Your app owns the document, the storage and the revisions. Keep the page and its plug-ins in your own codebase (npx rapier-embed plugins ./public/rapier fetches and verifies the reader's plug-ins); restyle the reader with --rapier-* CSS properties and your own fonts.

import {Rapier} from 'rapier-embed';
const editor = Rapier.mount(document.querySelector('#editor'), {
  sessionId, documentId,
  load: {content, filename: 'notes.md', revision},
  save: ({requestId, content, baseRevision}) => store.writeOnce({documentId, requestId, content, baseRevision}),
});

save returns {revision} once storage confirms the bytes, or throws Rapier.conflict(currentRevision). Pin a version at https://rapier.website/embed/<version>/rapier-document.html or .../rapier-reader.html. The embed skill documents the API, self-hosting and plug-ins; the embed contract is the wire protocol.

Markdown

Rapier writes CommonMark plus conventions other editors already read, with pictures inside the file: the standard, what other readers show, adopting it.

Source and self-hosting

src/ is the complete source of rapier.html; (cd src && node tools/build.mjs) rebuilds it byte for byte (build.json). npx wrangler deploy serves it with the included configuration. (cd src && RAPIER_PROFILE=document node tools/build.mjs) builds the smaller document editor without Notes, Draw and Paint; RAPIER_PROFILE=reader builds the read-only reader.

Run node --test src/tools/test-public.mjs with Node 22 to check concurrent source edits and Undo, authored HTML control boundaries, and hostile SVG filtering with drawing-data preservation. The tests need no browser, account, package install or network connection. The same checks run on every push and pull request in GitHub Actions.

Licence and contributing

AGPL-3.0-only with the stated terms; the reusable modules are MIT; a commercial licence is available (LICENSING.md). Issues and pull requests are welcome: CONTRIBUTING.md, SECURITY.md.

Related: rapier-plugins (the plugins and npm packages), rapier-jxl (the JPEG XL encoder), will (the Will standard).