Mdhero

A beautiful, native Markdown viewer and lightweight editor for macOS, Windows and Linux. ~8MB. Free. Open source.

Light mode Dark mode

Open local .md files, paste AI-generated markdown, or fetch from any public URL — and read or edit it the way it was meant to be.

Why MDHero

Markdown is where developers, writers, and AI live today — READMEs, Claude Code plans, LLM chat exports, notes, documentation. But opening a .md file in a code editor gives you ugly monospace text. Opening a web-based viewer means uploading your files. GitHub renders it beautifully but only if the file is in a repo.

MDHero is a native app for everything in between. Your files stay local. Rendering is instant. Edit in place when you need to. Works offline. Looks like it belongs on your machine.

Features

Reading

• Beautiful rendering — Apple-inspired typography, light & dark themes
• Syntax highlighting — 25+ languages via highlight.js
• Math & diagrams — KaTeX for equations, Mermaid for flowcharts
• Reader controls — adjust font, size, line height, width
• Zen mode — distraction-free full-screen reading
• Print/Export to PDF — File › Print or Cmd/Ctrl+P opens the native print dialog (print to paper or to PDF), with clean print styles

Editing (v0.2.0)

• Lightweight in-app editor — Cmd+E flips any local file into edit mode
• Save with `Cmd+S` — writes back to disk; the file watcher knows it was you and skips the reload
• Stays where you were — source-line scroll sync keeps your position across viewer ↔ raw ↔ edit
• Dirty indicator — • in the tab title and toolbar when you have unsaved changes
• Per-tab edit state — switch tabs and back; your edits are right where you left them

Navigation

• Multiple tabs — open many files, drag to reorder, Cmd+1–9 to switch
• Table of Contents — auto-generated sidebar with active heading tracking
• Search (Cmd+F) — with match highlighting
• Vim keys — j/k/gg/G/d/u/[/] for keyboard-first navigation
• Image lightbox — click to zoom, arrow keys for next/prev

Opening Files

• Local files — drag-drop, Cmd+O, "Open With" from Finder
• Pinned folders — quick access to markdown in your favorite directories
• Claude Code Plans — auto-discovers ~/.claude/plans/
• Open URL — fetch from GitHub, Gist, GitLab, Bitbucket, or any public URL
• Paste mode (Cmd+Shift+V) — render LLM output instantly, auto-unescapes \n
• Recent files — pick up where you left off, with reading progress per file