# 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:

1. **Getting a file** — receiving a TSX component, a Markdown doc, an HTML mockup
2. **Understanding the file** — seeing it rendered correctly, as it was intended
3. **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](https://mokingbird.xyz/about).

---

## Contact

- General: [[email protected]](mailto:[email protected])
- Support: [[email protected]](mailto:[email protected])
- GitHub: [github.com/mokingbird-xyz/mb-viewer-downloads](https://github.com/mokingbird-xyz/mb-viewer-downloads)

# Privacy Policy — MB Viewer

**MokingBird Oy** | Business ID: 3615646-1 | Finland

_Last updated: April 2026_

---

## Introduction

This Privacy Policy describes how MB Viewer ("the application," "the app") handles your data. MB Viewer is a desktop application developed and distributed by **MokingBird Oy**.

The short version: **MB Viewer collects no data during normal operation.** Your files stay on your device. We have no servers receiving your content, no analytics pipeline processing your behavior, and no way to see what you're doing inside the app.

This policy exists to be transparent about the very few data-related events that can occur (like optional update checks), so you understand exactly what the app does and does not do.

For questions, contact us at [[email protected]](mailto:[email protected]).

---

## 1. Data We Collect During App Operation

**None.**

When you use MB Viewer — opening files, editing them, switching themes, dragging tabs between windows — no data is transmitted anywhere. The app operates entirely on your local machine. There is no background process sending usage statistics, no analytics SDK tracking your sessions, and no crash reporter sending error logs to our servers.

Specifically, the following are **not collected**:

- Files you open or edit
- File contents, names, or paths
- Your usage patterns or session duration
- Error logs or crash reports
- Hardware or OS information
- IP address or location

---

## 2. Local Preferences Stored on Your Device

To maintain your settings between sessions, MB Viewer stores the following data **locally on your device only**:

- Theme preferences (light/dark/auto)
- Editor theme selections
- Window and tab state
- Font and zoom preferences

This data never leaves your device. It is stored in a local configuration file and can be deleted by removing the app's configuration directory.

---

## 3. Optional Update Checks

MB Viewer may offer an option to check for new versions. If you initiate an update check (or if automatic update checks are enabled in Settings):

- The app makes a single HTTPS request to our release server (GitHub Releases)
- The request contains: current app version number, your operating system type (e.g., Windows, macOS, Linux)
- **No personal data is included** — no user ID, no IP logging by our systems, no device fingerprinting
- The response contains only: latest available version number and release notes

You can disable automatic update checks in Settings. Manual update checks are entirely optional.

---

## 4. Files You Open

Every file you open in MB Viewer stays on your device.

- TSX/JSX files are transpiled locally using Babel Standalone (bundled inside the app)
- Markdown is rendered locally using a bundled renderer
- HTML files are displayed in a sandboxed iframe running locally
- JSON, CSS, JavaScript, SVG, and images are processed entirely in memory on your machine

No file content is sent to MokingBird servers, cloud services, or any third party as a result of using MB Viewer.

---

## 5. No Telemetry, No Analytics

MB Viewer contains no telemetry or analytics components of any kind. If optional diagnostic telemetry is ever introduced in a future version, it will be:

- Explicitly documented in this policy and in release notes
- Opt-in where required by law
- Limited to technical diagnostics only (no behavioral tracking, no file content)

MB Viewer contains no telemetry or analytics components of any kind currently. We do not use:

- Google Analytics
- Mixpanel, Amplitude, or similar analytics platforms
- Sentry or similar crash reporting services
- Any other data collection SDK

If you want to know exactly what network requests MB Viewer makes, you can use a network monitor — you will find only update check requests (if enabled) and any external resources loaded by HTML files you open inside the app (which are your files, not ours).

---

## 6. Data Sharing

We may use service providers for website hosting, binary distribution, and support communications. These providers receive only the minimum data required for service delivery and are not permitted to use your data for unrelated commercial purposes.

We do not sell personal data.

---

## 7. International Transfers

MokingBird Oy is based in Finland, within the EU. Where infrastructure services involve data processing outside the EU/EEA, we apply applicable GDPR safeguards.

---

## 8. Third-Party Components

MB Viewer is built using open-source components including Electron, React, Vite, Babel Standalone, and KaTeX. These components are bundled inside the app and do not independently contact external services during normal operation.

When you open an HTML file that references external resources (e.g., fonts from Google Fonts, or scripts from a CDN), those resources are loaded by the file you opened — not by MB Viewer's own systems. This is equivalent to opening that HTML file in any web browser.

---

## 9. Website (mbviewer.mokingbird.xyz)

The MB Viewer website uses standard web server logging (Netlify hosting). When you visit the website, standard server logs (IP address, browser type, page visited, timestamp) may be recorded for up to 30 days for security and error monitoring purposes.

We aim to use privacy-friendly, cookieless analytics. If analytics are enabled on the website, they will not track individuals and will not use cookies.

---

## 10. Your Rights Under GDPR

As a user in the European Union, you have rights under the General Data Protection Regulation including:

- **Right of access** — Request information about any personal data we hold
- **Right to erasure** — Request deletion of your personal data
- **Right to object** — Object to processing of your data

Since MB Viewer collects no personal data during app operation, most of these rights are satisfied by the app's design. For any privacy requests related to website data or download records, contact [[email protected]](mailto:[email protected]).

---

## 11. Children's Privacy

MB Viewer is a general-purpose developer tool. It is not directed at children under 13. We do not knowingly collect personal information from children. Since the app collects no personal data at all, there is no data at risk. Parents who have concerns about their child using MB Viewer may contact us at [[email protected]](mailto:[email protected]).

---

## 12. Changes to This Policy

If we update this Privacy Policy, we will update the "Last updated" date at the top and publish the new version on the MB Viewer website. For significant changes, we will note them in the app's release notes.

---

## 13. Contact

**MokingBird Oy**
Business ID: 3615646-1
Finland

- Privacy: [[email protected]](mailto:[email protected])
- Support: [[email protected]](mailto:[email protected])
- General: [[email protected]](mailto:[email protected])

---

# Terms of Service — MB Viewer

**MokingBird Oy** | Business ID: 3615646-1 | Finland

_Last updated: April 2026_

---

## 1. Acceptance of Terms

By downloading, installing, or using MB Viewer ("the application," "the software"), you agree to be bound by these Terms of Service ("Terms"). If you do not agree to these Terms, do not download or use MB Viewer.

These Terms constitute a legal agreement between you and **MokingBird Oy**, a company registered in Finland (Business ID: 3615646-1).

---

## 2. Description of Service

MB Viewer is a free, offline-first desktop application for viewing and editing files including TSX, JSX, HTML, Markdown, JSON, CSS, JavaScript, SVG, images, and plain text. The application is built on Electron and runs locally on your device. It does not require an internet connection for core functionality.

MB Viewer is distributed:
- Through the official website: [mbviewer.mokingbird.xyz](https://mbviewer.mokingbird.xyz)
- Through the official GitHub releases page: [github.com/mokingbird-xyz/mb-viewer-downloads](https://github.com/mokingbird-xyz/mb-viewer-downloads)

**Only download MB Viewer from these official sources.** MokingBird is not responsible for any harm resulting from software downloaded from unofficial or third-party sources.

---

## 3. License

### 3.1 Free License

Subject to these Terms, MokingBird Oy grants you a **non-exclusive, non-transferable, revocable license** to:

- Download and install MB Viewer on devices you own or control
- Use MB Viewer for personal and commercial purposes
- Use MB Viewer to view, edit, and preview files in your work

### 3.2 Restrictions

You may **not**:

- Sell, sublicense, or distribute MB Viewer without prior written permission from MokingBird Oy
- Modify, decompile, reverse engineer, or disassemble the application (except as permitted by applicable law)
- Remove or alter any copyright notices, branding, or proprietary notices in the application
- Use MB Viewer in any way that violates applicable laws or regulations
- Represent MB Viewer as your own product

### 3.3 Future Premium Features

MB Viewer is currently free for all features. MokingBird Oy reserves the right to introduce premium features in future versions that may require a license purchase or subscription. Any such changes will be clearly communicated before they take effect, and existing free features will remain free.

---

## 4. Downloading and Installation

MB Viewer is provided as a downloadable file (`.exe` for Windows, `.dmg` for macOS, `.AppImage` for Linux). Installation instructions are available on the official website.

By downloading MB Viewer, you confirm that:
- You are at least 13 years of age, or have parental consent
- You have the legal authority to install software on the device
- You are not located in a jurisdiction where downloading or using this software is prohibited

---

## 5. Your Files and Data

Files you open in MB Viewer remain entirely your property. MokingBird Oy has no access to the files you view or edit. Nothing is transmitted to MokingBird servers as a result of opening or editing files. Your data is yours.

See our [Privacy Policy](https://mbviewer.mokingbird.xyz/privacypolicy) for full details.

---

## 6. Updates

MokingBird Oy may release updates to MB Viewer that include new features, bug fixes, or security patches. Updates are available from the official GitHub releases page. You are not obligated to update, but we recommend staying current for the best experience and security.

If automatic update checks are enabled, the app will notify you when a new version is available. Updating requires downloading and installing the new version manually from the official source.

---

## 7. Disclaimer of Warranties

**MB Viewer is provided "as is" and "as available" without warranties of any kind**, either express or implied. To the fullest extent permitted by applicable law, MokingBird Oy disclaims all warranties, including but not limited to:

- Warranties of merchantability or fitness for a particular purpose
- Warranties that the application will be error-free or uninterrupted
- Warranties regarding the accuracy of file rendering or output

The rendering of files in MB Viewer (TSX previews, Markdown output, HTML sandboxes) is provided for convenience and preview purposes. Do not rely solely on MB Viewer's rendering for production decisions without independent verification.

---

## 8. Limitation of Liability

To the maximum extent permitted by Finnish law and EU law, MokingBird Oy shall not be liable for:

- Any indirect, incidental, special, consequential, or punitive damages
- Loss of data, profits, or business opportunities arising from your use of MB Viewer
- Damages resulting from files opened or processed using the application
- Any damages exceeding the amount you have paid to MokingBird Oy in the twelve months preceding the claim (which, for free users, is zero)

---

## 9. Intellectual Property

MB Viewer, including its source code, design, branding, and documentation, is the intellectual property of MokingBird Oy. The MokingBird name, logo, and MB Viewer name are trademarks of MokingBird Oy.

MB Viewer incorporates open-source components (Electron, React, Vite, Babel, KaTeX) which remain governed by their respective open-source licenses.

---

## 10. Indemnity

You agree to indemnify and hold harmless MokingBird Oy and its affiliates, officers, and employees from any claims, damages, losses, or expenses (including reasonable legal fees) arising from your misuse of MB Viewer, violation of these Terms, or infringement of any third-party rights.

---

## 11. Termination

Your license to use MB Viewer terminates immediately if you breach these Terms. To "uninstall" MB Viewer and end your use: delete the application file from your device. No deregistration process is required.

MokingBird Oy reserves the right to discontinue distribution of MB Viewer at any time, with reasonable notice provided through the official website and GitHub repository.

---

## 12. Governing Law

These Terms are governed by the laws of **Finland** and applicable **European Union** law. Any disputes arising from these Terms or your use of MB Viewer shall be subject to the exclusive jurisdiction of Finnish courts.

---

## 13. Changes to These Terms

MokingBird Oy may update these Terms from time to time. We will notify users by updating the "Last updated" date and publishing the new Terms on the official website. Continued use of MB Viewer after changes constitutes acceptance of the updated Terms.

---

## 14. Contact

For legal or terms-related inquiries:

**MokingBird Oy**
Business ID: 3615646-1
Finland

- Legal: [[email protected]](mailto:[email protected])
- General: [[email protected]](mailto:[email protected])
- Support: [[email protected]](mailto:[email protected])

---

_This document is a working baseline and should be reviewed by legal counsel before production publication._

Here's a scenario most developers know well. You're working with an AI assistant — Claude, ChatGPT, Gemini — and it generates a beautiful TSX component. Or a Markdown document. Or an HTML mockup. You download it. Now what?

You open a terminal, navigate to the right folder, run `npm install`, wait for packages, start the dev server, and finally... see a 400 error because you forgot to set up the right dependencies. That, or you paste it into a code editor that shows you the raw text but not what it actually renders as.

For a file that took three seconds to generate, it now takes fifteen minutes to preview.

**MB Viewer was built to fix exactly this.**

---

## Enter MB Viewer

MB Viewer is a free, offline-first desktop application that renders files the way they're meant to look — immediately, with no setup, no npm, no build process, and no internet connection required.

Download it (one file, under 5MB), run it, and you're done. Drag a TSX file in and see the live React component. Drop a Markdown document and get beautifully rendered output, including math equations. Open an HTML mockup and see it rendered in a full sandboxed preview. View a JSON config in a collapsible tree. Preview SVGs and images alongside code.

One app. Every format. Zero configuration.

Since its first release, MB Viewer has been downloaded over **800 times** by developers and designers who were tired of juggling tools for different file types.

---

## What Can You Open?

MB Viewer currently supports the following file formats natively:

| Format | What you get |
|--------|-------------|
| `.tsx` / `.jsx` | Live React component preview — full hooks, state, and effects |
| `.html` / `.htm` | Sandboxed iframe — full HTML/CSS/JS rendering |
| `.md` / `.markdown` | GitHub Flavored Markdown with KaTeX math, Mermaid diagrams, and syntax highlighting |
| `.mmd` / `.mermaid` | Rendered Mermaid diagram — flowcharts, sequence, ER, Gantt, state machines, and 12+ more |
| `.json` | Pretty-printed view with collapsible tree |
| `.css` | Syntax-highlighted code view |
| `.js` / `.ts` | Syntax-highlighted code view |
| `.svg` | Rendered vector graphics |
| `.txt` | Clean formatted text view |
| Images | PNG, JPG, GIF, WebP — responsive display |

No plugins. No extensions. No "install this codec." Every format opens the same way: drop it in, see it rendered.

---

## Under the Hood

MB Viewer isn't just a fancy file picker. It's built on a modern, carefully chosen tech stack:

- **Electron 39** — battle-tested cross-platform desktop runtime
- **React 19** — the UI itself is a React application
- **Vite 7** — fast build system powering development
- **Babel Standalone** — the TSX transpiler runs entirely inside the app. No Node.js server. No external build step. Drop in a `.tsx` file and Babel processes it right there in memory.
- **KaTeX** — offline math rendering. Every `$...$` inline equation and `$$...$$` block equation in your Markdown files renders perfectly without touching the internet.
- **Mermaid** — offline diagram rendering. Flowcharts, sequence diagrams, ER diagrams, Gantt charts, state machines, git graphs, and 12+ diagram types render inside `.md` files and as standalone `.mmd` files. Bundled locally — no CDN, no internet.

The result is an app that feels instant because it actually is. There's no network round trip, no compilation waiting on a server, no cold start penalty. Everything runs locally.

---

## Designed for Developers and Researchers

MB Viewer's tab and window system is built for serious multi-file workflows.

You can open **unlimited tabs** — each with its own files, view mode, theme, and zoom level. Each tab is fully independent. You can have a TSX preview in one tab, a Markdown document in another, and an HTML mockup in a third, all in the same window.

**Drag a tab out** of the window and it becomes a new independent MB Viewer window. Then **drag tabs between windows** — cross-window tab dragging landed in v2.9.0 and makes multi-monitor workflows genuinely useful. You can maintain separate workspaces across two screens, drag files between them freely, and each window remembers its own state.

Need to compare two files side by side? Switch to **Double View**. Need four files simultaneously? **Quad View** puts them in a 2×2 grid. Switch between modes freely — your files are preserved.

---

## Themes and Customization

MB Viewer uses a **3-layer independent theme system**:

1. **App theme** — Light or Dark, per tab
2. **Editor theme** — 8 choices per file, set independently for each file in a multi-view layout
3. **Font settings** — family and size, per preference

This means you can have one tab in dark mode with a Monokai editor theme, and another tab in light mode with a GitHub-style editor theme. The customization is per-tab, not global — because different files often look better in different contexts.

---

## Privacy by Design

MB Viewer collects **zero data**. No analytics. No telemetry. No crash reports. No user registration.

The app works entirely offline. Files you open never leave your machine. Babel transpiles your TSX in memory. KaTeX renders your math locally. The only network activity that ever occurs is an optional update check — which you can disable — and that check contains no personal data.

For developers who work with sensitive documents — proprietary code, confidential designs, internal documentation — MB Viewer is safe to use with files you can't send to a cloud service.

---

## Real-World Use Cases

**Frontend developers previewing AI-generated components.** Claude generates a React component. Drop it into MB Viewer and see exactly how it renders before committing to your codebase. No npm install. No dev server.

**Technical writers reviewing Markdown documentation.** See your documentation rendered exactly as readers will see it — tables, code blocks, math equations, all formatted. Edit in split-screen and watch the preview update live.

**Designers checking HTML mockups.** Open HTML files from Figma exports, AI-generated mockups, or prototypes. See them rendered in a sandboxed environment without opening a browser.

**Researchers working with JSON datasets.** Open large JSON files and navigate them in a collapsible tree view instead of scrolling through raw text.

**Students and educators.** Open multiple lecture notes, code examples, and exercises side by side in Quad View. Edit and preview simultaneously.

---

## What's New in v3.0.0

**MB Viewer v3.0.0** ships three major updates:

- **Mermaid diagram rendering** — Flowcharts, sequence diagrams, ER diagrams, Gantt charts, and 12+ more diagram types now render directly inside `.md` files and as standalone `.mmd` / `.mermaid` files. Fully offline, bundled locally. Syntax errors are shown inline so you know exactly what to fix — no crash, no spinner.
- **HTML preview navigation fixed** — Clicking links inside HTML file previews no longer crashes the app. Hash links (`#section`) scroll smoothly in place. All other link clicks are safely blocked within the preview.
- **Ctrl+S now works on drag-and-drop files** — Files opened by drag-and-drop can now be saved directly with Ctrl+S, no dialog, no "file path invalid" error. Save As also opens in the correct directory automatically.

Previous major milestones:
- **v2.9.0** — Cross-window tab dragging. Drag tabs between any MB Viewer windows.
- **v2.8.0** — Tab ejection. Drag a tab out to create a new independent window.
- **v2.5.0** — Multi-view modes (Single, Double, Quad).

---

## Download Free Today

MB Viewer is completely free to download and use. No account required. No subscription. No limitations on usage.

Download for your platform from:
- **Official website**: [mbviewer.mokingbird.xyz](https://mbviewer.mokingbird.xyz)
- **GitHub releases**: [github.com/mokingbird-xyz/mb-viewer-downloads](https://github.com/mokingbird-xyz/mb-viewer-downloads)

Available for Windows (`.exe`), macOS Intel (`.dmg`), macOS Apple Silicon (`.dmg`), and Linux (`.AppImage`).

If you run into anything unexpected, or have a file format you'd like to see supported, reach out at [[email protected]](mailto:[email protected]). We read every message.