MDHero.
The Markdown viewer you can edit in.
Free, open source.
A free, open source markdown viewer and lightweight markdown editor. Native, under 8MB.
MDHero is a free, open-source Markdown viewer and lightweight editor — about 8MB, built with Tauri and Rust, fully offline with no accounts or telemetry. Open any .md file instantly, then press ⌘E to edit and ⌘S to save.
Windows 10+ (x64 or ARM64), macOS 12+ (Apple Silicon), and Linux as a .deb, .rpm or .AppImage. On Windows, bypass SmartScreen once on first run; macOS is Apple-notarized.Three reasons you'll leave it on your Dock.
Your files stay local
Everything runs on your machine. No uploads, no cloud, no accounts — total privacy. Open a .md file, read it or edit it, offline or on.
Beautiful by default
Apple-inspired typography with dark mode, syntax highlighting for 25+ languages, KaTeX math, and Mermaid diagrams.
Built for the AI era
Paste ChatGPT or Claude output directly — MDHero auto-detects and cleans up LLM formatting. Also reads Claude Code plans.
Everything a markdown file needs. Nothing it doesn't.
Small ideas that make a difference every time you open a markdown file — viewing or editing.
Open anything.
Local files, GitHub URLs, pasted markdown, or Claude Code plans — one app reads them all.
Quick actions
Pinned folders
View, Split, or Edit — one switch.
A real markdown editor built into the viewer. Move between View, Split, and Edit from a single control — Split puts the editor and a live preview side by side. Line numbers in the gutter, ⌘F find that works in every mode, and scroll position that follows you line by line. ⌘S saves, and MDHero warns before you discard unsaved changes.
Tabs, TOC, and your muscle memory.
Multiple tabs with drag-to-reorder. Table of Contents sidebar. Search with ⌘F. Vim keybindings when you want them.
A one-page overview of what we're building and why it matters to the people using it every day.
Three outcomes, each measurable within a quarter.
Syntax highlighting that reads like a book.
25+ languages with beautiful code blocks. Copy button on hover. Dark and light themes that agree on what a string should look like.
Equations and flowcharts, rendered inline.
KaTeX renders LaTeX equations. Mermaid renders flowcharts, sequence diagrams, and more — with no plugins, no extra steps.
Paste raw LLM output. Read real markdown.
MDHero auto-detects escaped \n characters and stray backslashes in LLM output and renders clean markdown — no manual cleanup.
\n
Right-click anything. Ask the model.
Select a word or paragraph and right-click — send it to ChatGPT, Claude, Perplexity, Google, or Wikipedia in one click. URL-based, no API keys, no telemetry. Each provider holds your own saved prompts ("Explain this clearly:", "Summarize:") for reuse, configurable in Settings.
Markdown viewers vary widely in how they handle tokenization for syntax highlighting, which affects rendering speed on large files.
Pin your folders. Open with one click.
Pin frequently-used directories for instant access to every markdown file inside — no more hunting through Finder.
Pinned folders
Recent files
Turn a markdown file into slides.
Add marp: true to the front matter and MDHero opens the document as a native slideshow — arrow keys, Space, Home and End, with optional page numbers. No Marp CLI, no export step, no browser.
Three things we're shipping, and why they matter.
Change the file. It's already updated.
Every open tab tracks its file on disk — including the ones in the background. Edit in another editor, pull a branch, or regenerate docs, and MDHero is already showing the new version. Unsaved edits are never clobbered: the tab flags the change with ↻ and Save asks first. Close the app and your tabs come back in the same order.
The version on screen matches the version on disk, without a keystroke.
Press Space. It's already rendered.
On macOS, MDHero adds its own Quick Look extension. Select a .md file in Finder, hit Space, and you get headings, tables, syntax-highlighted code, KaTeX math and Mermaid diagrams — without opening the app. No plugin, no Homebrew, no Terminal: install MDHero, open it once, done.
The library for web and native user interfaces.
MDHero vs Typora, Obsidian, and VS Code.
The short version: ~8MB instead of 90–300MB, free instead of $14.99, and a focused viewer-and-editor instead of a full IDE or knowledge base.
| Markdown app | MDHero | Typora | Obsidian | VS Code |
|---|---|---|---|---|
| Price | Free | $14.99 | Free | Free |
| Open source | Yes (MIT) | No | No | Yes |
| App size | ~8MB | ~90MB | ~180MB | ~300MB |
| Built with | Tauri + Rust | Native | Electron | Electron |
| Primary mode | Viewer + editor | Editor | Knowledge base | Code editor |
| Presentation mode (Marp) | Built in | No | Plugin | Extension |
| LLM paste mode | Yes | No | No | No |
| AI Lookup (right-click) | Yes | No | No | No |
| Mac, Windows & Linux | Yes | Yes | Yes | Yes |
Sizes are approximate install footprints. Typora is a one-time $14.99 purchase; Obsidian is free for personal use with paid sync/publish add-ons. Full platform breakdowns on the Mac and Windows pages, and an honest 7-app roundup in Best Free Markdown Viewers in 2026.
For when your hands don't want to leave the keyboard.
⌘ becomes Ctrl — and the app labels its own hints that way too.Open source, MIT licensed.
A free markdown viewer and lightweight markdown editor — open source under MIT, crafted for people who live in their markdown.
MDHero is free and always will be. If it saved you time, a coffee keeps it maintained.
From the MDHero blog
Built with in open source.