Markdown Lens

A privacy-first, in-memory Markdown viewer. Drop in your .md files and read them beautifully rendered, with Claude-like fidelity. Everything happens in your browser: there is no backend, nothing is uploaded, and nothing is saved. Refresh the tab and it is all gone by design.

Features

• Private by design: in-memory only, no backend, no storage of file content.
• Multi-file: upload several files and switch between them in the sidebar.
• GitHub-Flavored Markdown: tables, task lists, strikethrough, autolinks.
• LaTeX math with KaTeX, inline and block.
• Code blocks with a language label, syntax highlighting, and a copy button.
• Light and dark themes; the code block stays dark in both.
• Responsive down to mobile, with a slide-in file drawer.

Tech stack

Vite, React 18, and TypeScript (strict). react-markdown with remark-gfm, remark-math, rehype-katex, and rehype-highlight. Tailwind CSS with @tailwindcss/typography, and lucide-react for icons.

Run it

npm install      # install dependencies
npm run dev      # start the local dev server
npm run build    # produce the static production bundle (dist/)
npm run preview  # preview the built static bundle
npm run lint     # lint

The build is a static bundle: deploy dist/ to any static host with zero server cost.

Accepted files

.md, .markdown, and .txt, up to 5 MB each. Duplicate names are disambiguated rather than overwritten.

Fonts

All fonts are self-hosted; nothing is loaded from a CDN.

• Reading and headings: Merriweather (self-hosted via @fontsource), with Lastik as a self-hosted fallback (bundled in src/assets/fonts).
• UI and chrome: Poppins.
• Code: the system monospace stack (ui-monospace, JetBrains Mono, Menlo).

Live

markdown-lens-ten.vercel.app