# mdshare

A markdown editor whose document lives entirely in the URL. Type markdown on the left, see it rendered on the right, and share the page by copying the link: the text is compressed and encoded into the URL fragment, so there is no server, no account, and nothing is uploaded.

**Live: <https://concept-collection.github.io/mdshare/>**

## What it renders

- LaTeX math, inline (`$...$`) and display (`$$...$$`), via remark-math and KaTeX
- Fenced code blocks with per-language syntax highlighting (highlight.js) and a copy button
- GitHub-flavored markdown: tables, task lists, strikethrough, footnotes, autolinks
- Mermaid diagrams in ` ```mermaid ` fences (the mermaid library is loaded lazily, only when a document uses one)

Raw HTML in the document is deliberately rendered as text rather than passed through. Since any document can arrive via a shared link, HTML passthrough would let a link author run script in the viewer's browser.

## How the URL encoding works

The document is stored in the hash fragment as

```
#base64url( version byte + DEFLATE(utf8 text) )
```

The fragment is never sent to any server, and base64url needs no percent-escaping, so links survive copy and paste through chat clients and email. A one-byte version header leaves room to change the encoding later without breaking old links. Editing updates the URL in place (via `replaceState`, debounced) so the address bar always holds a shareable link; the length of the current URL is shown in the top bar.

A typical page of prose with a few equations compresses to a URL of roughly one to two thousand characters. Browsers handle URLs far longer than that, but some other software truncates very long links, so the length indicator is worth a glance before sharing a large document.

## Development

```bash
npm install
npm run dev     # local dev server
npm run build   # typecheck + production build to dist/
```

Deployment to GitHub Pages is automatic on push to `main` via `.github/workflows/deploy.yml`.