MDHero — Common questions, answered straight.

MDHero is a free, open-source markdown viewer and lightweight editor for macOS, Windows and Linux, distributed under the MIT license. The desktop app is ~8MB, runs entirely offline, and will stay free forever — there is no paid tier and no plan to add one for the local app.

The source code is on GitHub at github.com/vaibhav-kakde-in/mdhero, and every release is built from public GitHub Actions CI. You can audit it, fork it, or build it from source.

MDHero collects no usage data. The only network call is a once-per-24-hours update check to mdhero.app/api/version that sends your current version and OS family (darwin, win32 or linux).

There are no device IDs, no IP storage, no file contents, no analytics scripts, and no third-party trackers. All markdown files stay on your machine. The update endpoint source is public so the disclosure is verifiable — see src/pages/api/version.ts in the website repo.

MDHero is roughly 20× smaller than the alternatives — ~8MB versus Typora ~90MB, Obsidian ~180MB, and VS Code ~300MB — because it is built with Tauri and Rust instead of Electron.

It is free and open source under MIT, whereas Typora costs $14.99 and is closed source. Unlike Obsidian or VS Code, MDHero is a focused viewer with a lightweight in-place editor (Cmd+E to edit, Cmd+S to save), not a full knowledge base or IDE. See our detailed comparison on best free markdown viewers in 2026.

MDHero does not include its own sync. It reads .md files from wherever they live, so placing your markdown folder in iCloud Drive, Dropbox, OneDrive, Syncthing, or a git repository lets your Mac, Windows and Linux installations all see the same files. Live reload means a file changed by sync on one machine repaints in an open tab on another.

This avoids creating another proprietary sync silo on top of services that already solve the problem well, and it means your notes are never locked into MDHero — they are just plain markdown text files.

On macOS (Apple Silicon, M1 through M4), download the .dmg from mdhero.app/mac, drag MDHero to Applications, and double-click. The DMG is notarized and stapled as of v0.2.10, so it opens with no Gatekeeper warning at all.

On Windows 10 or 11, download the .exe or .msi installer — x64 or arm64 — from mdhero.app/windows and click More info then Run anyway past the SmartScreen warning once.

On Linux, install the .deb with apt, the .rpm with dnf, or chmod +x the .AppImage and run it — see mdhero.app/linux. After the first launch, every platform runs normally from then on.

Detailed step-by-step guides: macOS install · Windows install · Linux install.

Yes. Since v0.2.9 MDHero ships pre-built Linux packages — a .deb for Debian and Ubuntu, a .rpm for Fedora and openSUSE, and an .AppImage that runs on any distro without installing.

Every format is built for both x64 and arm64, in the same CI run as the macOS and Windows binaries, so Linux gets the same features at the same time. Building from source is still supported. Downloads and per-distro install commands: mdhero.app/linux.

Yes. Every open tab watches its own file, including tabs in the background, so editing a document in another editor, pulling a git branch, or regenerating docs updates MDHero without a keystroke.

If a file changes while you have unsaved edits in it, your edits are kept, the tab is marked as changed, and Save asks before overwriting. Tabs also reopen after a restart in the same order with the same active tab — switch that off in Settings → Behavior if you'd rather start clean.

Yes. MDHero has an LLM paste mode (Cmd+Shift+V on Mac, Ctrl+Shift+V on Windows) that auto-detects escaped \n characters from AI clipboard output and renders clean markdown.

This solves the common problem where copying from ChatGPT, Claude, or Gemini produces literal \n newlines and stray backslashes when pasted into other apps. MDHero also reads Claude Code plans directly from ~/.claude/plans. See our deep-dive on fixing ChatGPT paste formatting.

Yes. MDHero runs fully offline — it reads and renders local markdown files with no internet connection required.

The only network request it ever makes is a once-per-24-hours update check to mdhero.app/api/version. Block that endpoint and the app still works completely; nothing else depends on the network, and no file contents ever leave your machine. This makes it suitable for air-gapped and corporate environments.

MDHero opens .md, .markdown, and .mdx files, plus GitHub URLs, raw pasted markdown (Cmd+Shift+V), and Claude Code plan files from ~/.claude/plans.

It renders GitHub-Flavored Markdown including tables, task lists, footnotes, syntax-highlighted code in 25+ languages, KaTeX math, and Mermaid diagrams. It is a viewer and lightweight editor, not a converter — it does not currently export to PDF or Word.

Yes. MDHero is fully open source under the MIT license, so every line of code is auditable on GitHub.

The macOS DMG is signed with an Apple Developer ID and, as of v0.2.10, notarized and stapled by Apple (Apple has scanned it for malware, and the ticket travels with the file so the check works offline). The macOS, Windows and Linux binaries are all built automatically on public GitHub Actions CI from public source, each published with a signature file — no manual step where something could be tampered with. It collects no telemetry and requires no account.