About MB Viewer
One App. Every File. Zero Setup.
MB Viewer is a free, offline-first desktop application for instantly viewing and editing design and development files — no npm install, no build tools, no configuration required. Drop in a file, see it rendered beautifully in under a second.
Built by MokingBird — part of The Everything Lab — MB Viewer started with a frustration every developer knows: you get a file from Claude or ChatGPT, and you need three different tools just to see what it looks like. A browser for HTML, a code editor for TSX, a markdown renderer for documentation. MB Viewer replaces all of them with one portable app.
Version: v3.0.0 Downloads: 800+ Platforms: Windows · macOS (Intel + Apple Silicon) · Linux
What Is MB Viewer?
MB Viewer is an Electron-based desktop application built with React 19 and Vite 7. It renders files locally — no internet connection required after installation. Everything from Babel transpilation for TSX/JSX to KaTeX for math equations runs bundled inside the app.
You can open TSX components as live previews, render Markdown with full GitHub Flavored Markdown support including LaTeX math, view HTML pages in a sandboxed iframe, pretty-print JSON with a tree view, preview SVGs, and view images — all inside one app, in one window, across unlimited tabs.
Product Mission
MB Viewer exists to remove friction between three moments:
- Getting a file — receiving a TSX component, a Markdown doc, an HTML mockup
- Understanding the file — seeing it rendered correctly, as it was intended
- Acting on the file — editing, reviewing, sharing it
No setup-heavy environment should be required for common preview tasks.
Why We Built It
When AI code assistants became mainstream, a new problem emerged: AI generates files faster than you can view them. TSX components, Markdown documentation, HTML mockups, JSON configs — each needs a different tool to preview properly.
MB Viewer was built to solve exactly this. One portable app (under 5MB) that handles the most common file formats a developer or designer encounters when working with AI tools. No installation wizard. No account. No cloud. Just download and run.
It's also useful in restricted environments — air-gapped machines, secure networks, offline workstations — where cloud-based tools are blocked or unavailable. MB Viewer needs no internet connection for any core feature.
Key Features
Multi-Tab, Multi-Window Workspaces
- Open unlimited tabs, each with its own files, view mode, and theme
- Drag a tab out to create a new independent window
- Drag tabs between windows — cross-window drag is fully supported
- Each tab remembers its own state (files, zoom, theme, view mode)
Professional File Rendering
- TSX/JSX — Live React component preview powered by Babel standalone. No npm. Renders hooks, state, and effects.
- HTML — Full sandboxed iframe rendering with CSS and JS support
- Markdown — GitHub Flavored Markdown with KaTeX math (inline and block LaTeX), syntax highlighting for 20+ languages, tables, task lists
- JSON — Pretty-printed with collapsible tree view
- CSS / JavaScript / SVG — Syntax-highlighted code view
- Images — PNG, JPG, GIF, WebP with responsive display
- Plain text — Clean reading view
Multi-View Modes
- Single View — one file, full window
- Double View — two files side by side
- Quad View — four files in a 2×2 grid
3-Layer Independent Theme System
- App theme (Light/Dark) per tab
- 8 editor themes per file
- Font family and size selection
- Per-slot zoom (50%–200%)
Live Split-Screen Editing
Edit any file and see the preview update in real time. Full split-screen mode with 8 independent editor themes.
Technology
| Component | Technology |
|---|---|
| Desktop runtime | Electron 39 |
| UI framework | React 19 |
| Build tool | Vite 7 |
| TSX/JSX transpilation | Babel Standalone (bundled) |
| Math rendering | KaTeX (bundled, offline) |
| Syntax highlighting | Bundled highlighter |
Everything is bundled. Nothing phones home.
Privacy & Security
MB Viewer collects no data:
- No analytics
- No telemetry
- No crash reports
- No user registration
- No internet connection required for any core feature
- Files you open never leave your machine
Optional update checks (user-initiated) make a single version comparison request — no personal data included.
Part of MokingBird
MB Viewer is part of the MokingBird ecosystem — The Everything Lab. We build software that works for you, respects your privacy, and doesn't lock you in.
Learn more about MokingBird at mokingbird.xyz/about.
Contact
- General: info@mbviewer.mokingbird.xyz
- Support: support@mbviewer.mokingbird.xyz
- GitHub: github.com/mokingbird-xyz/mb-viewer-downloads